SECTION-A
Question:-01
Let
G
G
G G G be a group of order 10 and
G
′
G
′
G^(‘) G’ G ′ be a group of order 6. Examine whether there exists a homomorphism of
G
G
G G G onto
G
′
G
′
G^(‘) G’ G ′ .
Answer:
To determine whether there exists a surjective (onto) homomorphism
ϕ
:
G
→
G
′
ϕ
:
G
→
G
′
phi:G rarrG^(‘) \phi: G \to G’ ϕ : G → G ′ , where
|
G
|
=
10
|
G
|
=
10
|G|=10 |G| = 10 | G | = 10 and
|
G
′
|
=
6
|
G
′
|
=
6
|G^(‘)|=6 |G’| = 6 | G ′ | = 6 , we analyze the implications of such a homomorphism using the
First Isomorphism Theorem .
First Isomorphism Theorem :
If
ϕ
ϕ
phi \phi ϕ is a surjective homomorphism, then:
G
/
ker
(
ϕ
)
≅
G
′
.
G
/
ker
(
ϕ
)
≅
G
′
.
G//ker(phi)~=G^(‘). G / \ker(\phi) \cong G’. G / ker ( ϕ ) ≅ G ′ .
This implies:
|
G
|
/
|
ker
(
ϕ
)
|
=
|
G
′
|
⟹
10
/
|
ker
(
ϕ
)
|
=
6.
|
G
|
/
|
ker
(
ϕ
)
|
=
|
G
′
|
⟹
10
/
|
ker
(
ϕ
)
|
=
6.
|G|//|ker(phi)|=|G^(‘)|Longrightarrow10//|ker(phi)|=6. |G| / |\ker(\phi)| = |G’| \implies 10 / |\ker(\phi)| = 6. | G | / | ker ( ϕ ) | = | G ′ | ⟹ 10 / | ker ( ϕ ) | = 6.
Solving for
|
ker
(
ϕ
)
|
|
ker
(
ϕ
)
|
|ker(phi)| |\ker(\phi)| | ker ( ϕ ) | , we get:
|
ker
(
ϕ
)
|
=
10
6
=
5
3
.
|
ker
(
ϕ
)
|
=
10
6
=
5
3
.
|ker(phi)|=(10)/(6)=(5)/(3). |\ker(\phi)| = \frac{10}{6} = \frac{5}{3}. | ker ( ϕ ) | = 10 6 = 5 3 .
However,
|
ker
(
ϕ
)
|
|
ker
(
ϕ
)
|
|ker(phi)| |\ker(\phi)| | ker ( ϕ ) | must be an integer because it represents the order of a subgroup of
G
G
G G G . Since
5
3
5
3
(5)/(3) \frac{5}{3} 5 3 is not an integer, this leads to a contradiction.
Lagrange’s Theorem Verification :
The possible orders of
ker
(
ϕ
)
ker
(
ϕ
)
ker(phi) \ker(\phi) ker ( ϕ ) (subgroups of
G
G
G G G ) are the divisors of 10: 1, 2, 5, 10.
If
|
ker
(
ϕ
)
|
=
1
|
ker
(
ϕ
)
|
=
1
|ker(phi)|=1 |\ker(\phi)| = 1 | ker ( ϕ ) | = 1 , then
|
G
′
|
=
10
≠
6
|
G
′
|
=
10
≠
6
|G^(‘)|=10!=6 |G’| = 10 \neq 6 | G ′ | = 10 ≠ 6 .
If
|
ker
(
ϕ
)
|
=
2
|
ker
(
ϕ
)
|
=
2
|ker(phi)|=2 |\ker(\phi)| = 2 | ker ( ϕ ) | = 2 , then
|
G
′
|
=
5
≠
6
|
G
′
|
=
5
≠
6
|G^(‘)|=5!=6 |G’| = 5 \neq 6 | G ′ | = 5 ≠ 6 .
If
|
ker
(
ϕ
)
|
=
5
|
ker
(
ϕ
)
|
=
5
|ker(phi)|=5 |\ker(\phi)| = 5 | ker ( ϕ ) | = 5 , then
|
G
′
|
=
2
≠
6
|
G
′
|
=
2
≠
6
|G^(‘)|=2!=6 |G’| = 2 \neq 6 | G ′ | = 2 ≠ 6 .
If
|
ker
(
ϕ
)
|
=
10
|
ker
(
ϕ
)
|
=
10
|ker(phi)|=10 |\ker(\phi)| = 10 | ker ( ϕ ) | = 10 , then
|
G
′
|
=
1
≠
6
|
G
′
|
=
1
≠
6
|G^(‘)|=1!=6 |G’| = 1 \neq 6 | G ′ | = 1 ≠ 6 .
None of these cases satisfy
|
G
′
|
=
6
|
G
′
|
=
6
|G^(‘)|=6 |G’| = 6 | G ′ | = 6 .
Conclusion :
Since there is no subgroup
ker
(
ϕ
)
ker
(
ϕ
)
ker(phi) \ker(\phi) ker ( ϕ ) of
G
G
G G G such that
G
/
ker
(
ϕ
)
G
/
ker
(
ϕ
)
G//ker(phi) G / \ker(\phi) G / ker ( ϕ ) has order 6,
no surjective homomorphism exists from
G
G
G G G to
G
′
G
′
G^(‘) G’ G ′ .
Hence,there does not exist a surjective homomorphism from a group
G
G
G G G of order 10 onto a group
G
′
G
′
G^(‘) G’ G ′ of order 6.}
Question:-01 (b)
Express the ideal
4
Z
+
6
Z
4
Z
+
6
Z
4Z+6Z 4Z + 6Z 4 Z + 6 Z as a principal ideal in the integral domain
Z
Z
Z Z Z .
Answer:
To express the ideal
4
Z
+
6
Z
4
Z
+
6
Z
4Z+6Z 4\mathbb{Z} + 6\mathbb{Z} 4 Z + 6 Z as a principal ideal in the integral domain
Z
Z
Z \mathbb{Z} Z , we can follow these steps:
Understand the Sum of Ideals :
The sum of two ideals
4
Z
4
Z
4Z 4\mathbb{Z} 4 Z and
6
Z
6
Z
6Z 6\mathbb{Z} 6 Z in
Z
Z
Z \mathbb{Z} Z is the ideal generated by the union of their generators. In other words:
4
Z
+
6
Z
=
{
4
a
+
6
b
∣
a
,
b
∈
Z
}
4
Z
+
6
Z
=
{
4
a
+
6
b
∣
a
,
b
∈
Z
}
4Z+6Z={4a+6b∣a,b inZ} 4\mathbb{Z} + 6\mathbb{Z} = \{4a + 6b \mid a, b \in \mathbb{Z}\} 4 Z + 6 Z = { 4 a + 6 b ∣ a , b ∈ Z }
Find the Greatest Common Divisor (GCD) :
The ideal
4
Z
+
6
Z
4
Z
+
6
Z
4Z+6Z 4\mathbb{Z} + 6\mathbb{Z} 4 Z + 6 Z is generated by the greatest common divisor (GCD) of 4 and 6. This is a fundamental property of ideals in
Z
Z
Z \mathbb{Z} Z .
Compute the GCD of 4 and 6:
gcd
(
4
,
6
)
=
2
gcd
(
4
,
6
)
=
2
gcd(4,6)=2 \gcd(4, 6) = 2 gcd ( 4 , 6 ) = 2
Express as a Principal Ideal :
Since the GCD is 2, the ideal
4
Z
+
6
Z
4
Z
+
6
Z
4Z+6Z 4\mathbb{Z} + 6\mathbb{Z} 4 Z + 6 Z can be expressed as the principal ideal generated by 2:
4
Z
+
6
Z
=
2
Z
4
Z
+
6
Z
=
2
Z
4Z+6Z=2Z 4\mathbb{Z} + 6\mathbb{Z} = 2\mathbb{Z} 4 Z + 6 Z = 2 Z
Final Answer :
2
Z
2
Z
2Z \boxed{2\mathbb{Z}} 2 Z
Question:-01 (c)
Test the convergence of the series
∑
n
=
1
∞
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
,
x
>
0.
∑
n
=
1
∞
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
,
x
>
0.
sum_(n=1)^(oo)(1*3*5dots(2n-1))/(2*4*6dots(2n))*(x^(2n+1))/(2n+1),quad x > 0. \sum_{n=1}^{\infty} \frac{1 \cdot 3 \cdot 5 \ldots (2n-1)}{2 \cdot 4 \cdot 6 \ldots (2n)} \cdot \frac{x^{2n+1}}{2n+1}, \quad x > 0. ∑ n = 1 ∞ 1 ⋅ 3 ⋅ 5 … ( 2 n − 1 ) 2 ⋅ 4 ⋅ 6 … ( 2 n ) ⋅ x 2 n + 1 2 n + 1 , x > 0.
Answer:
To test the convergence of the series
∑
n
=
1
∞
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
,
x
>
0
,
∑
n
=
1
∞
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
,
x
>
0
,
sum_(n=1)^(oo)(1*3*5dots(2n-1))/(2*4*6dots(2n))*(x^(2n+1))/(2n+1),quad x > 0, \sum_{n=1}^{\infty} \frac{1 \cdot 3 \cdot 5 \ldots (2n-1)}{2 \cdot 4 \cdot 6 \ldots (2n)} \cdot \frac{x^{2n+1}}{2n+1}, \quad x > 0, ∑ n = 1 ∞ 1 ⋅ 3 ⋅ 5 … ( 2 n − 1 ) 2 ⋅ 4 ⋅ 6 … ( 2 n ) ⋅ x 2 n + 1 2 n + 1 , x > 0 ,
we can use the Ratio Test , which is suitable for series with factorial-like terms.
Step 1: Simplify the General Term
Let the general term be:
a
n
=
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
.
a
n
=
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
⋅
x
2
n
+
1
2
n
+
1
.
a_(n)=(1*3*5dots(2n-1))/(2*4*6dots(2n))*(x^(2n+1))/(2n+1). a_n = \frac{1 \cdot 3 \cdot 5 \ldots (2n-1)}{2 \cdot 4 \cdot 6 \ldots (2n)} \cdot \frac{x^{2n+1}}{2n+1}. a n = 1 ⋅ 3 ⋅ 5 … ( 2 n − 1 ) 2 ⋅ 4 ⋅ 6 … ( 2 n ) ⋅ x 2 n + 1 2 n + 1 .
We can rewrite the product of odd and even numbers using double factorials or ratios of factorials:
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
=
(
2
n
−
1
)
!
!
(
2
n
)
!
!
=
(
2
n
)
!
4
n
(
n
!
)
2
.
1
⋅
3
⋅
5
…
(
2
n
−
1
)
2
⋅
4
⋅
6
…
(
2
n
)
=
(
2
n
−
1
)
!
!
(
2
n
)
!
!
=
(
2
n
)
!
4
n
(
n
!
)
2
.
(1*3*5dots(2n-1))/(2*4*6dots(2n))=((2n-1)!!)/((2n)!!)=((2n)!)/(4^(n)(n!)^(2)). \frac{1 \cdot 3 \cdot 5 \ldots (2n-1)}{2 \cdot 4 \cdot 6 \ldots (2n)} = \frac{(2n-1)!!}{(2n)!!} = \frac{(2n)!}{4^n (n!)^2}. 1 ⋅ 3 ⋅ 5 … ( 2 n − 1 ) 2 ⋅ 4 ⋅ 6 … ( 2 n ) = ( 2 n − 1 ) ! ! ( 2 n ) ! ! = ( 2 n ) ! 4 n ( n ! ) 2 .
However, for the Ratio Test, it’s sufficient to consider the ratio of consecutive terms.
Step 2: Apply the Ratio Test
Compute the ratio of consecutive terms:
a
n
+
1
a
n
=
(
2
(
n
+
1
)
−
1
)
!
!
(
2
(
n
+
1
)
)
!
!
⋅
x
2
(
n
+
1
)
+
1
2
(
n
+
1
)
+
1
(
2
n
−
1
)
!
!
(
2
n
)
!
!
⋅
x
2
n
+
1
2
n
+
1
.
a
n
+
1
a
n
=
(
2
(
n
+
1
)
−
1
)
!
!
(
2
(
n
+
1
)
)
!
!
⋅
x
2
(
n
+
1
)
+
1
2
(
n
+
1
)
+
1
(
2
n
−
1
)
!
!
(
2
n
)
!
!
⋅
x
2
n
+
1
2
n
+
1
.
(a_(n+1))/(a_(n))=(((2(n+1)-1)!!)/((2(n+1))!!)*(x^(2(n+1)+1))/(2(n+1)+1))/(((2n-1)!!)/((2n)!!)*(x^(2n+1))/(2n+1)). \frac{a_{n+1}}{a_n} = \frac{\frac{(2(n+1)-1)!!}{(2(n+1))!!} \cdot \frac{x^{2(n+1)+1}}{2(n+1)+1}}{\frac{(2n-1)!!}{(2n)!!} \cdot \frac{x^{2n+1}}{2n+1}}. a n + 1 a n = ( 2 ( n + 1 ) − 1 ) ! ! ( 2 ( n + 1 ) ) ! ! ⋅ x 2 ( n + 1 ) + 1 2 ( n + 1 ) + 1 ( 2 n − 1 ) ! ! ( 2 n ) ! ! ⋅ x 2 n + 1 2 n + 1 .
Simplify the ratio:
a
n
+
1
a
n
=
(
2
n
+
1
)
(
2
n
+
2
)
⋅
x
2
n
+
3
2
n
+
3
⋅
2
n
+
1
x
2
n
+
1
=
(
2
n
+
1
)
2
(
2
n
+
2
)
(
2
n
+
3
)
⋅
x
2
.
a
n
+
1
a
n
=
(
2
n
+
1
)
(
2
n
+
2
)
⋅
x
2
n
+
3
2
n
+
3
⋅
2
n
+
1
x
2
n
+
1
=
(
2
n
+
1
)
2
(
2
n
+
2
)
(
2
n
+
3
)
⋅
x
2
.
(a_(n+1))/(a_(n))=((2n+1))/((2n+2))*(x^(2n+3))/(2n+3)*(2n+1)/(x^(2n+1))=((2n+1)^(2))/((2n+2)(2n+3))*x^(2). \frac{a_{n+1}}{a_n} = \frac{(2n+1)}{(2n+2)} \cdot \frac{x^{2n+3}}{2n+3} \cdot \frac{2n+1}{x^{2n+1}} = \frac{(2n+1)^2}{(2n+2)(2n+3)} \cdot x^2. a n + 1 a n = ( 2 n + 1 ) ( 2 n + 2 ) ⋅ x 2 n + 3 2 n + 3 ⋅ 2 n + 1 x 2 n + 1 = ( 2 n + 1 ) 2 ( 2 n + 2 ) ( 2 n + 3 ) ⋅ x 2 .
Take the limit as
n
→
∞
n
→
∞
n rarr oo n \to \infty n → ∞ :
lim
n
→
∞
a
n
+
1
a
n
=
lim
n
→
∞
(
2
n
+
1
)
2
(
2
n
+
2
)
(
2
n
+
3
)
⋅
x
2
=
lim
n
→
∞
4
n
2
+
4
n
+
1
4
n
2
+
10
n
+
6
⋅
x
2
=
x
2
.
lim
n
→
∞
a
n
+
1
a
n
=
lim
n
→
∞
(
2
n
+
1
)
2
(
2
n
+
2
)
(
2
n
+
3
)
⋅
x
2
=
lim
n
→
∞
4
n
2
+
4
n
+
1
4
n
2
+
10
n
+
6
⋅
x
2
=
x
2
.
lim_(n rarr oo)(a_(n+1))/(a_(n))=lim_(n rarr oo)((2n+1)^(2))/((2n+2)(2n+3))*x^(2)=lim_(n rarr oo)(4n^(2)+4n+1)/(4n^(2)+10 n+6)*x^(2)=x^(2). \lim_{n \to \infty} \frac{a_{n+1}}{a_n} = \lim_{n \to \infty} \frac{(2n+1)^2}{(2n+2)(2n+3)} \cdot x^2 = \lim_{n \to \infty} \frac{4n^2 + 4n + 1}{4n^2 + 10n + 6} \cdot x^2 = x^2. lim n → ∞ a n + 1 a n = lim n → ∞ ( 2 n + 1 ) 2 ( 2 n + 2 ) ( 2 n + 3 ) ⋅ x 2 = lim n → ∞ 4 n 2 + 4 n + 1 4 n 2 + 10 n + 6 ⋅ x 2 = x 2 .
Step 3: Determine Convergence
By the Ratio Test:
If
lim
n
→
∞
|
a
n
+
1
a
n
|
<
1
lim
n
→
∞
a
n
+
1
a
n
<
1
lim_(n rarr oo)|(a_(n+1))/(a_(n))| < 1 \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right| < 1 lim n → ∞ | a n + 1 a n | < 1 , the series converges.
If
lim
n
→
∞
|
a
n
+
1
a
n
|
>
1
lim
n
→
∞
a
n
+
1
a
n
>
1
lim_(n rarr oo)|(a_(n+1))/(a_(n))| > 1 \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right| > 1 lim n → ∞ | a n + 1 a n | > 1 , the series diverges.
If
lim
n
→
∞
|
a
n
+
1
a
n
|
=
1
lim
n
→
∞
a
n
+
1
a
n
=
1
lim_(n rarr oo)|(a_(n+1))/(a_(n))|=1 \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right| = 1 lim n → ∞ | a n + 1 a n | = 1 , the test is inconclusive.
Here,
lim
n
→
∞
a
n
+
1
a
n
=
x
2
lim
n
→
∞
a
n
+
1
a
n
=
x
2
lim_(n rarr oo)(a_(n+1))/(a_(n))=x^(2) \lim_{n \to \infty} \frac{a_{n+1}}{a_n} = x^2 lim n → ∞ a n + 1 a n = x 2 , so:
The series converges if
x
2
<
1
x
2
<
1
x^(2) < 1 x^2 < 1 x 2 < 1 (i.e.,
0
<
x
<
1
0
<
x
<
1
0 < x < 1 0 < x < 1 0 < x < 1 ).
The series diverges if
x
2
>
1
x
2
>
1
x^(2) > 1 x^2 > 1 x 2 > 1 (i.e.,
x
>
1
x
>
1
x > 1 x > 1 x > 1 ).
The test is inconclusive if
x
=
1
x
=
1
x=1 x = 1 x = 1 .
Step 4: Check the Boundary Case
x
=
1
x
=
1
x=1 x = 1 x = 1
For
x
=
1
x
=
1
x=1 x = 1 x = 1 , the series becomes:
∑
n
=
1
∞
(
2
n
−
1
)
!
!
(
2
n
)
!
!
⋅
1
2
n
+
1
.
∑
n
=
1
∞
(
2
n
−
1
)
!
!
(
2
n
)
!
!
⋅
1
2
n
+
1
.
sum_(n=1)^(oo)((2n-1)!!)/((2n)!!)*(1)/(2n+1). \sum_{n=1}^{\infty} \frac{(2n-1)!!}{(2n)!!} \cdot \frac{1}{2n+1}. ∑ n = 1 ∞ ( 2 n − 1 ) ! ! ( 2 n ) ! ! ⋅ 1 2 n + 1 .
Using Gauss’s Test or Raabe’s Test , we can show that this series diverges. Alternatively, note that:
(
2
n
−
1
)
!
!
(
2
n
)
!
!
∼
1
π
n
(by Stirling’s approximation)
,
(
2
n
−
1
)
!
!
(
2
n
)
!
!
∼
1
π
n
(by Stirling’s approximation)
,
((2n-1)!!)/((2n)!!)∼(1)/(sqrt(pi n))quad(by Stirling’s approximation), \frac{(2n-1)!!}{(2n)!!} \sim \frac{1}{\sqrt{\pi n}} \quad \text{(by Stirling’s approximation)}, ( 2 n − 1 ) ! ! ( 2 n ) ! ! ∼ 1 π n (by Stirling’s approximation) ,
so the general term behaves like
1
2
n
3
/
2
1
2
n
3
/
2
(1)/(2n^(3//2)) \frac{1}{2n^{3/2}} 1 2 n 3 / 2 , and the series diverges by comparison with the harmonic series.
Final Conclusion
The series converges for
0
<
x
<
1
0
<
x
<
1
0 < x < 1 0 < x < 1 0 < x < 1 .
The series diverges for
x
≥
1
x
≥
1
x >= 1 x \geq 1 x ≥ 1 .
The series converges for
0
<
x
<
1
and diverges for
x
≥
1.
The series converges for
0
<
x
<
1
and diverges for
x
≥
1.
“The series converges for “0 < x < 1” and diverges for “x >= 1. \boxed{\text{The series converges for } 0 < x < 1 \text{ and diverges for } x \geq 1.} The series converges for 0 < x < 1 and diverges for x ≥ 1.
Question:-01 (d)
State the sufficient conditions for a function
f
(
z
)
=
f
(
x
+
i
y
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
f
(
z
)
=
f
(
x
+
i
y
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
f(z)=f(x+iy)=u(x,y)+iv(x,y) f(z) = f(x + iy) = u(x, y) + i v(x, y) f ( z ) = f ( x + i y ) = u ( x , y ) + i v ( x , y ) to be analytic in its domain. Hence, show that
f
(
z
)
=
log
z
f
(
z
)
=
log
z
f(z)=log z f(z) = \log z f ( z ) = log z is analytic in its domain and find
d
f
d
z
d
f
d
z
(df)/(dz) \frac{df}{dz} d f d z .
Answer:
Sufficient Conditions for Analyticity
A function
f
(
z
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
f
(
z
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
f(z)=u(x,y)+iv(x,y) f(z) = u(x, y) + i v(x, y) f ( z ) = u ( x , y ) + i v ( x , y ) is
analytic (holomorphic) in a domain
D
D
D D D if the following conditions hold:
Existence of Partial Derivatives :
The partial derivatives
∂
u
∂
x
,
∂
u
∂
y
,
∂
v
∂
x
,
∂
v
∂
y
∂
u
∂
x
,
∂
u
∂
y
,
∂
v
∂
x
,
∂
v
∂
y
(del u)/(del x),(del u)/(del y),(del v)/(del x),(del v)/(del y) \frac{\partial u}{\partial x}, \frac{\partial u}{\partial y}, \frac{\partial v}{\partial x}, \frac{\partial v}{\partial y} ∂ u ∂ x , ∂ u ∂ y , ∂ v ∂ x , ∂ v ∂ y exist and are continuous in
D
D
D D D .
Cauchy-Riemann Equations :
The functions
u
(
x
,
y
)
u
(
x
,
y
)
u(x,y) u(x,y) u ( x , y ) and
v
(
x
,
y
)
v
(
x
,
y
)
v(x,y) v(x,y) v ( x , y ) satisfy:
∂
u
∂
x
=
∂
v
∂
y
,
∂
u
∂
y
=
−
∂
v
∂
x
.
∂
u
∂
x
=
∂
v
∂
y
,
∂
u
∂
y
=
−
∂
v
∂
x
.
(del u)/(del x)=(del v)/(del y),quad(del u)/(del y)=-(del v)/(del x). \frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \quad \frac{\partial u}{\partial y} = -\frac{\partial v}{\partial x}. ∂ u ∂ x = ∂ v ∂ y , ∂ u ∂ y = − ∂ v ∂ x .
If these conditions hold, then
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) is differentiable in
D
D
D D D , and its derivative is given by:
f
′
(
z
)
=
∂
u
∂
x
+
i
∂
v
∂
x
=
∂
v
∂
y
−
i
∂
u
∂
y
.
f
′
(
z
)
=
∂
u
∂
x
+
i
∂
v
∂
x
=
∂
v
∂
y
−
i
∂
u
∂
y
.
f^(‘)(z)=(del u)/(del x)+i(del v)/(del x)=(del v)/(del y)-i(del u)/(del y). f'(z) = \frac{\partial u}{\partial x} + i \frac{\partial v}{\partial x} = \frac{\partial v}{\partial y} – i \frac{\partial u}{\partial y}. f ′ ( z ) = ∂ u ∂ x + i ∂ v ∂ x = ∂ v ∂ y − i ∂ u ∂ y .
Analyticity of
f
(
z
)
=
log
z
f
(
z
)
=
log
z
f(z)=log z f(z) = \log z f ( z ) = log z
The complex logarithm is defined as:
log
z
=
ln
|
z
|
+
i
arg
z
,
log
z
=
ln
|
z
|
+
i
arg
z
,
log z=ln |z|+i arg z, \log z = \ln |z| + i \arg z, log z = ln | z | + i arg z ,
where:
ln
|
z
|
ln
|
z
|
ln |z| \ln |z| ln | z | is the natural logarithm of the modulus,
arg
z
arg
z
arg z \arg z arg z is the argument (angle) of
z
z
z z z .
Let
z
=
x
+
i
y
=
r
e
i
θ
z
=
x
+
i
y
=
r
e
i
θ
z=x+iy=re^(i theta) z = x + iy = re^{i\theta} z = x + i y = r e i θ , where
r
=
x
2
+
y
2
r
=
x
2
+
y
2
r=sqrt(x^(2)+y^(2)) r = \sqrt{x^2 + y^2} r = x 2 + y 2 and
θ
=
arg
z
θ
=
arg
z
theta=arg z \theta = \arg z θ = arg z . Then:
log
z
=
ln
r
+
i
θ
=
1
2
ln
(
x
2
+
y
2
)
+
i
arctan
(
y
x
)
.
log
z
=
ln
r
+
i
θ
=
1
2
ln
(
x
2
+
y
2
)
+
i
arctan
y
x
.
log z=ln r+i theta=(1)/(2)ln(x^(2)+y^(2))+i arctan((y)/(x)). \log z = \ln r + i \theta = \frac{1}{2} \ln(x^2 + y^2) + i \arctan\left(\frac{y}{x}\right). log z = ln r + i θ = 1 2 ln ( x 2 + y 2 ) + i arctan ( y x ) .
Thus, we identify:
u
(
x
,
y
)
=
1
2
ln
(
x
2
+
y
2
)
,
v
(
x
,
y
)
=
arctan
(
y
x
)
.
u
(
x
,
y
)
=
1
2
ln
(
x
2
+
y
2
)
,
v
(
x
,
y
)
=
arctan
y
x
.
u(x,y)=(1)/(2)ln(x^(2)+y^(2)),quad v(x,y)=arctan((y)/(x)). u(x, y) = \frac{1}{2} \ln(x^2 + y^2), \quad v(x, y) = \arctan\left(\frac{y}{x}\right). u ( x , y ) = 1 2 ln ( x 2 + y 2 ) , v ( x , y ) = arctan ( y x ) .
1. Check the Cauchy-Riemann Equations
Compute the partial derivatives:
∂
u
∂
x
=
x
x
2
+
y
2
,
∂
u
∂
y
=
y
x
2
+
y
2
,
∂
u
∂
x
=
x
x
2
+
y
2
,
∂
u
∂
y
=
y
x
2
+
y
2
,
(del u)/(del x)=(x)/(x^(2)+y^(2)),quad(del u)/(del y)=(y)/(x^(2)+y^(2)), \frac{\partial u}{\partial x} = \frac{x}{x^2 + y^2}, \quad \frac{\partial u}{\partial y} = \frac{y}{x^2 + y^2}, ∂ u ∂ x = x x 2 + y 2 , ∂ u ∂ y = y x 2 + y 2 ,
∂
v
∂
x
=
−
y
x
2
+
y
2
,
∂
v
∂
y
=
x
x
2
+
y
2
.
∂
v
∂
x
=
−
y
x
2
+
y
2
,
∂
v
∂
y
=
x
x
2
+
y
2
.
(del v)/(del x)=(-y)/(x^(2)+y^(2)),quad(del v)/(del y)=(x)/(x^(2)+y^(2)). \frac{\partial v}{\partial x} = \frac{-y}{x^2 + y^2}, \quad \frac{\partial v}{\partial y} = \frac{x}{x^2 + y^2}. ∂ v ∂ x = − y x 2 + y 2 , ∂ v ∂ y = x x 2 + y 2 .
Now verify:
∂
u
∂
x
=
x
x
2
+
y
2
=
∂
v
∂
y
,
∂
u
∂
x
=
x
x
2
+
y
2
=
∂
v
∂
y
,
(del u)/(del x)=(x)/(x^(2)+y^(2))=(del v)/(del y), \frac{\partial u}{\partial x} = \frac{x}{x^2 + y^2} = \frac{\partial v}{\partial y}, ∂ u ∂ x = x x 2 + y 2 = ∂ v ∂ y ,
∂
u
∂
y
=
y
x
2
+
y
2
=
−
(
−
y
x
2
+
y
2
)
=
−
∂
v
∂
x
.
∂
u
∂
y
=
y
x
2
+
y
2
=
−
−
y
x
2
+
y
2
=
−
∂
v
∂
x
.
(del u)/(del y)=(y)/(x^(2)+y^(2))=-((-y)/(x^(2)+y^(2)))=-(del v)/(del x). \frac{\partial u}{\partial y} = \frac{y}{x^2 + y^2} = -\left( \frac{-y}{x^2 + y^2} \right) = -\frac{\partial v}{\partial x}. ∂ u ∂ y = y x 2 + y 2 = − ( − y x 2 + y 2 ) = − ∂ v ∂ x .
Thus, the Cauchy-Riemann equations hold .
2. Continuity of Partial Derivatives
The partial derivatives are continuous everywhere except at
z
=
0
z
=
0
z=0 z = 0 z = 0 , where
log
z
log
z
log z \log z log z is not defined. Hence,
log
z
log
z
log z \log z log z is analytic in its domain
C
∖
{
0
}
C
∖
{
0
}
C\\{0} \mathbb{C} \setminus \{0\} C ∖ { 0 } .
Derivative of
log
z
log
z
log z \log z log z
Using the derivative formula for analytic functions:
f
′
(
z
)
=
∂
u
∂
x
+
i
∂
v
∂
x
=
x
x
2
+
y
2
+
i
(
−
y
x
2
+
y
2
)
=
x
−
i
y
x
2
+
y
2
.
f
′
(
z
)
=
∂
u
∂
x
+
i
∂
v
∂
x
=
x
x
2
+
y
2
+
i
−
y
x
2
+
y
2
=
x
−
i
y
x
2
+
y
2
.
f^(‘)(z)=(del u)/(del x)+i(del v)/(del x)=(x)/(x^(2)+y^(2))+i((-y)/(x^(2)+y^(2)))=(x-iy)/(x^(2)+y^(2)). f'(z) = \frac{\partial u}{\partial x} + i \frac{\partial v}{\partial x} = \frac{x}{x^2 + y^2} + i \left( \frac{-y}{x^2 + y^2} \right) = \frac{x – iy}{x^2 + y^2}. f ′ ( z ) = ∂ u ∂ x + i ∂ v ∂ x = x x 2 + y 2 + i ( − y x 2 + y 2 ) = x − i y x 2 + y 2 .
But
x
2
+
y
2
=
|
z
|
2
x
2
+
y
2
=
|
z
|
2
x^(2)+y^(2)=|z|^(2) x^2 + y^2 = |z|^2 x 2 + y 2 = | z | 2 , and
x
−
i
y
=
z
―
x
−
i
y
=
z
¯
x-iy= bar(z) x – iy = \overline{z} x − i y = z ― , so:
f
′
(
z
)
=
z
―
|
z
|
2
=
1
z
.
f
′
(
z
)
=
z
¯
|
z
|
2
=
1
z
.
f^(‘)(z)=( bar(z))/(|z|^(2))=(1)/(z). f'(z) = \frac{\overline{z}}{|z|^2} = \frac{1}{z}. f ′ ( z ) = z ― | z | 2 = 1 z .
Thus:
d
d
z
log
z
=
1
z
.
d
d
z
log
z
=
1
z
.
(d)/(dz)log z=(1)/(z). \frac{d}{dz} \log z = \frac{1}{z}. d d z log z = 1 z .
Final Answer
log
z
is analytic in
C
∖
{
0
}
,
and its derivative is
d
d
z
log
z
=
1
z
.
log
z
is analytic in
C
∖
{
0
}
,
and its derivative is
d
d
z
log
z
=
1
z
.
log z” is analytic in “C\\{0},” and its derivative is “(d)/(dz)log z=(1)/(z). \boxed{\log z \text{ is analytic in } \mathbb{C} \setminus \{0\}, \text{ and its derivative is } \frac{d}{dz} \log z = \frac{1}{z}.} log z is analytic in C ∖ { 0 } , and its derivative is d d z log z = 1 z .
Question:-01 (e)
A person requires 24, 24, and 20 units of chemicals
A
A
A A A ,
B
B
B B B , and
C
C
C C C respectively for his garden. Product
P
P
P P P contains 2, 4, and 1 units of chemicals
A
A
A A A ,
B
B
B B B , and
C
C
C C C respectively per jar, and product
Q
Q
Q Q Q contains 2, 1, and 5 units of chemicals
A
A
A A A ,
B
B
B B B , and
C
C
C C C respectively per jar. If a jar of
P
P
P P P costs ₹30 and a jar of
Q
Q
Q Q Q costs ₹50, then how many jars of each should be purchased in order to minimize the cost and meet the requirements?
Answer:
Problem Statement
A person requires:
24 units of chemical
A
A
A A A ,
24 units of chemical
B
B
B B B ,
20 units of chemical
C
C
C C C .
Products Available:
Product
P
P
P P P (per jar):
2 units of
A
A
A A A ,
4 units of
B
B
B B B ,
1 unit of
C
C
C C C .
Cost: ₹30 per jar.
Product
Q
Q
Q Q Q (per jar):
2 units of
A
A
A A A ,
1 unit of
B
B
B B B ,
5 units of
C
C
C C C .
Cost: ₹50 per jar.
Goal: Determine the number of jars of
P
P
P P P and
Q
Q
Q Q Q to purchase to
minimize cost while meeting the chemical requirements.
Step 1: Define Variables
Let:
x
x
x x x = number of jars of
P
P
P P P ,
y
y
y y y = number of jars of
Q
Q
Q Q Q .
The total units of each chemical must satisfy the requirements:
2
x
+
2
y
≥
24
⇒
x
+
y
≥
12.
2
x
+
2
y
≥
24
⇒
x
+
y
≥
12.
2x+2y >= 24quad=>quad x+y >= 12. 2x + 2y \geq 24 \quad \Rightarrow \quad x + y \geq 12. 2 x + 2 y ≥ 24 ⇒ x + y ≥ 12.
4
x
+
y
≥
24.
4
x
+
y
≥
24.
4x+y >= 24. 4x + y \geq 24. 4 x + y ≥ 24.
x
+
5
y
≥
20.
x
+
5
y
≥
20.
x+5y >= 20. x + 5y \geq 20. x + 5 y ≥ 20.
Non-negativity:
x
≥
0
,
y
≥
0.
x
≥
0
,
y
≥
0.
x >= 0,quad y >= 0. x \geq 0, \quad y \geq 0. x ≥ 0 , y ≥ 0.
Step 3: Objective Function
We want to minimize the total cost :
Cost
=
30
x
+
50
y
.
Cost
=
30
x
+
50
y
.
“Cost”=30 x+50 y. \text{Cost} = 30x + 50y. Cost = 30 x + 50 y .
Step 4: Solve the System of Inequalities
We find the feasible region by solving the inequalities:
From
x
+
y
≥
12
x
+
y
≥
12
x+y >= 12 x + y \geq 12 x + y ≥ 12 :
If
x
=
0
x
=
0
x=0 x = 0 x = 0 ,
y
=
12
y
=
12
y=12 y = 12 y = 12 .
If
y
=
0
y
=
0
y=0 y = 0 y = 0 ,
x
=
12
x
=
12
x=12 x = 12 x = 12 .
From
4
x
+
y
≥
24
4
x
+
y
≥
24
4x+y >= 24 4x + y \geq 24 4 x + y ≥ 24 :
If
x
=
0
x
=
0
x=0 x = 0 x = 0 ,
y
=
24
y
=
24
y=24 y = 24 y = 24 .
If
y
=
0
y
=
0
y=0 y = 0 y = 0 ,
x
=
6
x
=
6
x=6 x = 6 x = 6 .
From
x
+
5
y
≥
20
x
+
5
y
≥
20
x+5y >= 20 x + 5y \geq 20 x + 5 y ≥ 20 :
If
x
=
0
x
=
0
x=0 x = 0 x = 0 ,
y
=
4
y
=
4
y=4 y = 4 y = 4 .
If
y
=
0
y
=
0
y=0 y = 0 y = 0 ,
x
=
20
x
=
20
x=20 x = 20 x = 20 .
Intersection Points (Vertices of Feasible Region):
Step 5: Evaluate Cost at Critical Points
Compute
Cost
=
30
x
+
50
y
Cost
=
30
x
+
50
y
“Cost”=30 x+50 y \text{Cost} = 30x + 50y Cost = 30 x + 50 y at each feasible vertex:
At
(
4
,
8
)
(
4
,
8
)
(4,8) (4, 8) ( 4 , 8 ) :
30
(
4
)
+
50
(
8
)
=
120
+
400
=₹
520.
30
(
4
)
+
50
(
8
)
=
120
+
400
=₹
520.
30(4)+50(8)=120+400=₹520. 30(4) + 50(8) = 120 + 400 = ₹520. ₹ 30 ( 4 ) + 50 ( 8 ) = 120 + 400 =₹ 520.
At
(
10
,
2
)
(
10
,
2
)
(10,2) (10, 2) ( 10 , 2 ) :
30
(
10
)
+
50
(
2
)
=
300
+
100
=₹
400.
30
(
10
)
+
50
(
2
)
=
300
+
100
=₹
400.
30(10)+50(2)=300+100=₹400. 30(10) + 50(2) = 300 + 100 = ₹400. ₹ 30 ( 10 ) + 50 ( 2 ) = 300 + 100 =₹ 400.
At
(
100
19
,
56
19
)
100
19
,
56
19
((100)/(19),(56)/(19)) \left( \frac{100}{19}, \frac{56}{19} \right) ( 100 19 , 56 19 ) :
30
(
100
19
)
+
50
(
56
19
)
=
3000
19
+
2800
19
=
5800
19
≈₹
305.26
.
30
100
19
+
50
56
19
=
3000
19
+
2800
19
=
5800
19
≈₹
305.26
.
30((100)/(19))+50((56)/(19))=(3000)/(19)+(2800)/(19)=(5800)/(19)≈₹305.26. 30 \left( \frac{100}{19} \right) + 50 \left( \frac{56}{19} \right) = \frac{3000}{19} + \frac{2800}{19} = \frac{5800}{19} \approx ₹305.26. ₹ 30 ( 100 19 ) + 50 ( 56 19 ) = 3000 19 + 2800 19 = 5800 19 ≈₹ 305.26 .
However,
x
x
x x x and
y
y
y y y must be integers (since you can’t buy a fraction of a jar). So, we check integer solutions near
(
100
19
,
56
19
)
≈
(
5.26
,
2.95
)
100
19
,
56
19
≈
(
5.26
,
2.95
)
((100)/(19),(56)/(19))~~(5.26,2.95) \left( \frac{100}{19}, \frac{56}{19} \right) \approx (5.26, 2.95) ( 100 19 , 56 19 ) ≈ ( 5.26 , 2.95 ) :
Try
(
5
,
3
)
(
5
,
3
)
(5,3) (5, 3) ( 5 , 3 ) :
Check constraints:
2
(
5
)
+
2
(
3
)
=
16
≥
24
?
No (16 < 24)
.
Not feasible.
2
(
5
)
+
2
(
3
)
=
16
≥
24
?
No (16 < 24)
.
Not feasible.
2(5)+2(3)=16 >= 24?quad”No (16 < 24)”.quad”Not feasible.” 2(5) + 2(3) = 16 \geq 24? \quad \text{No (16 < 24)}. \quad \text{Not feasible.} 2 ( 5 ) + 2 ( 3 ) = 16 ≥ 24 ? No (16 < 24) . Not feasible.
Try
(
6
,
2
)
(
6
,
2
)
(6,2) (6, 2) ( 6 , 2 ) :
Check constraints:
2
(
6
)
+
2
(
2
)
=
16
≥
24
?
No (16 < 24)
.
Not feasible.
2
(
6
)
+
2
(
2
)
=
16
≥
24
?
No (16 < 24)
.
Not feasible.
2(6)+2(2)=16 >= 24?quad”No (16 < 24)”.quad”Not feasible.” 2(6) + 2(2) = 16 \geq 24? \quad \text{No (16 < 24)}. \quad \text{Not feasible.} 2 ( 6 ) + 2 ( 2 ) = 16 ≥ 24 ? No (16 < 24) . Not feasible.
Try
(
6
,
6
)
(
6
,
6
)
(6,6) (6, 6) ( 6 , 6 ) :
Check constraints:
2
(
6
)
+
2
(
6
)
=
24
≥
24
(OK)
,
4
(
6
)
+
6
=
30
≥
24
(OK)
,
6
+
5
(
6
)
=
36
≥
20
(OK)
.
2
(
6
)
+
2
(
6
)
=
24
≥
24
(OK)
,
4
(
6
)
+
6
=
30
≥
24
(OK)
,
6
+
5
(
6
)
=
36
≥
20
(OK)
.
2(6)+2(6)=24 >= 24quad(OK),4(6)+6=30 >= 24quad(OK),6+5(6)=36 >= 20quad(OK). 2(6) + 2(6) = 24 \geq 24 \quad \text{(OK)}, \\
4(6) + 6 = 30 \geq 24 \quad \text{(OK)}, \\
6 + 5(6) = 36 \geq 20 \quad \text{(OK)}. 2 ( 6 ) + 2 ( 6 ) = 24 ≥ 24 (OK) , 4 ( 6 ) + 6 = 30 ≥ 24 (OK) , 6 + 5 ( 6 ) = 36 ≥ 20 (OK) .
Cost:
30
(
6
)
+
50
(
6
)
=
180
+
300
=₹
480.
30
(
6
)
+
50
(
6
)
=
180
+
300
=₹
480.
30(6)+50(6)=180+300=₹480. 30(6) + 50(6) = 180 + 300 = ₹480. ₹ 30 ( 6 ) + 50 ( 6 ) = 180 + 300 =₹ 480.
Try
(
4
,
8
)
(
4
,
8
)
(4,8) (4, 8) ( 4 , 8 ) : (Already computed: ₹520)
Try
(
10
,
2
)
(
10
,
2
)
(10,2) (10, 2) ( 10 , 2 ) : (Already computed: ₹400)
Best integer solution:
(
10
,
2
)
(
10
,
2
)
(10,2) (10, 2) ( 10 , 2 ) with cost
₹400 .
But wait, let’s check another integer point:
Try
(
8
,
4
)
(
8
,
4
)
(8,4) (8, 4) ( 8 , 4 ) :
Check constraints:
2
(
8
)
+
2
(
4
)
=
24
≥
24
(OK)
,
4
(
8
)
+
4
=
36
≥
24
(OK)
,
8
+
5
(
4
)
=
28
≥
20
(OK)
.
2
(
8
)
+
2
(
4
)
=
24
≥
24
(OK)
,
4
(
8
)
+
4
=
36
≥
24
(OK)
,
8
+
5
(
4
)
=
28
≥
20
(OK)
.
2(8)+2(4)=24 >= 24quad(OK),4(8)+4=36 >= 24quad(OK),8+5(4)=28 >= 20quad(OK). 2(8) + 2(4) = 24 \geq 24 \quad \text{(OK)}, \\
4(8) + 4 = 36 \geq 24 \quad \text{(OK)}, \\
8 + 5(4) = 28 \geq 20 \quad \text{(OK)}. 2 ( 8 ) + 2 ( 4 ) = 24 ≥ 24 (OK) , 4 ( 8 ) + 4 = 36 ≥ 24 (OK) , 8 + 5 ( 4 ) = 28 ≥ 20 (OK) .
Cost:
30
(
8
)
+
50
(
4
)
=
240
+
200
=₹
440.
30
(
8
)
+
50
(
4
)
=
240
+
200
=₹
440.
30(8)+50(4)=240+200=₹440. 30(8) + 50(4) = 240 + 200 = ₹440. ₹ 30 ( 8 ) + 50 ( 4 ) = 240 + 200 =₹ 440.
But
(
10
,
2
)
(
10
,
2
)
(10,2) (10, 2) ( 10 , 2 ) gives a lower cost (₹400) than
(
8
,
4
)
(
8
,
4
)
(8,4) (8, 4) ( 8 , 4 ) (₹440).
Verification of
(
10
,
2
)
(
10
,
2
)
(10,2) (10, 2) ( 10 , 2 ) :
Chemical
A
A
A A A :
2
(
10
)
+
2
(
2
)
=
24
2
(
10
)
+
2
(
2
)
=
24
2(10)+2(2)=24 2(10) + 2(2) = 24 2 ( 10 ) + 2 ( 2 ) = 24 (OK),
Chemical
B
B
B B B :
4
(
10
)
+
2
=
42
≥
24
4
(
10
)
+
2
=
42
≥
24
4(10)+2=42 >= 24 4(10) + 2 = 42 \geq 24 4 ( 10 ) + 2 = 42 ≥ 24 (OK),
Chemical
C
C
C C C :
10
+
5
(
2
)
=
20
≥
20
10
+
5
(
2
)
=
20
≥
20
10+5(2)=20 >= 20 10 + 5(2) = 20 \geq 20 10 + 5 ( 2 ) = 20 ≥ 20 (OK).
This is feasible and cheaper than other integer solutions.
Conclusion
The minimum cost is achieved by purchasing:
10 jars of
P
P
P P P ,
2 jars of
Q
Q
Q Q Q ,
with a total cost of ₹400 .
(
x
,
y
)
=
(
10
,
2
)
with a minimum cost of ₹400.
(
x
,
y
)
=
(
10
,
2
)
with a minimum cost of ₹400.
(x,y)=(10,2)” with a minimum cost of ₹400.” \boxed{(x, y) = (10, 2) \text{ with a minimum cost of ₹400.}} ₹ ( x , y ) = ( 10 , 2 ) with a minimum cost of ₹400.
Question:-02
(a) Prove that a non-commutative group of order
2
p
2
p
2p 2p 2 p , where
p
p
p p p is an odd prime, must have a subgroup of order
p
p
p p p .
Answer:
To prove that a non-commutative group
G
G
G G G of order
2
p
2
p
2p 2p 2 p , where
p
p
p p p is an odd prime, must have a subgroup of order
p
p
p p p , we can proceed as follows:
Step 1: Use Sylow’s Theorems
By Sylow’s First Theorem, since
p
p
p p p divides the order of
G
G
G G G (which is
2
p
2
p
2p 2p 2 p ), there exists at least one Sylow
p
p
p p p -subgroup of
G
G
G G G . Let
n
p
n
p
n_(p) n_p n p denote the number of Sylow
p
p
p p p -subgroups.
Step 2: Show
H
H
H H H is Normal
Since
n
p
=
1
n
p
=
1
n_(p)=1 n_p = 1 n p = 1 , the Sylow
p
p
p p p -subgroup
H
H
H H H is unique, and thus it is
normal in
G
G
G G G .
Step 3: Non-commutativity Implies
G
G
G G G is Not Cyclic
If
G
G
G G G were commutative, it would be isomorphic to the cyclic group
Z
2
p
Z
2
p
Z_(2p) \mathbb{Z}_{2p} Z 2 p , which has a unique subgroup of order
p
p
p p p . But
G
G
G G G is given to be
non-commutative , so it must be isomorphic to the
dihedral group
D
p
D
p
D_(p) D_p D p , which has the structure:
G
=
⟨
r
,
s
∣
r
p
=
s
2
=
e
,
s
r
s
=
r
−
1
⟩
,
G
=
⟨
r
,
s
∣
r
p
=
s
2
=
e
,
s
r
s
=
r
−
1
⟩
,
G=(:r,s∣r^(p)=s^(2)=e,srs=r^(-1):), G = \langle r, s \mid r^p = s^2 = e, srs = r^{-1} \rangle, G = ⟨ r , s ∣ r p = s 2 = e , s r s = r − 1 ⟩ ,
where:
⟨
r
⟩
⟨
r
⟩
(:r:) \langle r \rangle ⟨ r ⟩ is the cyclic subgroup of order
p
p
p p p ,
⟨
s
⟩
⟨
s
⟩
(:s:) \langle s \rangle ⟨ s ⟩ is a subgroup of order
2
2
2 2 2 .
Final Conclusion
Thus, in the non-commutative case,
G
G
G G G must have:
A normal subgroup
H
H
H H H of order
p
p
p p p (the Sylow
p
p
p p p -subgroup),
And another subgroup of order
2
2
2 2 2 , but the question focuses on the subgroup of order
p
p
p p p .
A non-commutative group of order
2
p
has a normal subgroup of order
p
.
A non-commutative group of order
2
p
has a normal subgroup of order
p
.
“A non-commutative group of order “2p” has a normal subgroup of order “p. \boxed{\text{A non-commutative group of order } 2p \text{ has a normal subgroup of order } p.} A non-commutative group of order 2 p has a normal subgroup of order p .
Question:-02 (b)
Using the method of Lagrange’s multipliers, find the minimum and maximum distances of the point
P
(
2
,
6
,
3
)
P
(
2
,
6
,
3
)
P(2,6,3) P(2, 6, 3) P ( 2 , 6 , 3 ) from the sphere
x
2
+
y
2
+
z
2
=
4
x
2
+
y
2
+
z
2
=
4
x^(2)+y^(2)+z^(2)=4 x^2 + y^2 + z^2 = 4 x 2 + y 2 + z 2 = 4 .
Answer:
To find the
minimum and maximum distances from the point
P
(
2
,
6
,
3
)
P
(
2
,
6
,
3
)
P(2,6,3) P(2, 6, 3) P ( 2 , 6 , 3 ) to the sphere
x
2
+
y
2
+
z
2
=
4
x
2
+
y
2
+
z
2
=
4
x^(2)+y^(2)+z^(2)=4 x^2 + y^2 + z^2 = 4 x 2 + y 2 + z 2 = 4 using
Lagrange multipliers , follow these steps:
Step 1: Define the Distance Function
The distance
D
D
D D D from
P
(
2
,
6
,
3
)
P
(
2
,
6
,
3
)
P(2,6,3) P(2, 6, 3) P ( 2 , 6 , 3 ) to a point
(
x
,
y
,
z
)
(
x
,
y
,
z
)
(x,y,z) (x, y, z) ( x , y , z ) on the sphere is given by:
D
=
(
x
−
2
)
2
+
(
y
−
6
)
2
+
(
z
−
3
)
2
.
D
=
(
x
−
2
)
2
+
(
y
−
6
)
2
+
(
z
−
3
)
2
.
D=sqrt((x-2)^(2)+(y-6)^(2)+(z-3)^(2)). D = \sqrt{(x – 2)^2 + (y – 6)^2 + (z – 3)^2}. D = ( x − 2 ) 2 + ( y − 6 ) 2 + ( z − 3 ) 2 .
To simplify computations, we minimize and maximize the squared distance :
D
2
=
(
x
−
2
)
2
+
(
y
−
6
)
2
+
(
z
−
3
)
2
.
D
2
=
(
x
−
2
)
2
+
(
y
−
6
)
2
+
(
z
−
3
)
2
.
D^(2)=(x-2)^(2)+(y-6)^(2)+(z-3)^(2). D^2 = (x – 2)^2 + (y – 6)^2 + (z – 3)^2. D 2 = ( x − 2 ) 2 + ( y − 6 ) 2 + ( z − 3 ) 2 .
Step 2: Set Up the Constraint
The point
(
x
,
y
,
z
)
(
x
,
y
,
z
)
(x,y,z) (x, y, z) ( x , y , z ) must lie on the sphere:
x
2
+
y
2
+
z
2
=
4.
x
2
+
y
2
+
z
2
=
4.
x^(2)+y^(2)+z^(2)=4. x^2 + y^2 + z^2 = 4. x 2 + y 2 + z 2 = 4.
Step 3: Apply the Method of Lagrange Multipliers
We introduce a Lagrange multiplier
λ
λ
lambda \lambda λ and set up the following system by taking partial derivatives:
∇
D
2
=
λ
∇
(
x
2
+
y
2
+
z
2
)
.
∇
D
2
=
λ
∇
(
x
2
+
y
2
+
z
2
)
.
gradD^(2)=lambda grad(x^(2)+y^(2)+z^(2)). \nabla D^2 = \lambda \nabla (x^2 + y^2 + z^2). ∇ D 2 = λ ∇ ( x 2 + y 2 + z 2 ) .
This gives:
2
(
x
−
2
)
=
λ
⋅
2
x
,
2
(
y
−
6
)
=
λ
⋅
2
y
,
2
(
z
−
3
)
=
λ
⋅
2
z
.
2
(
x
−
2
)
=
λ
⋅
2
x
,
2
(
y
−
6
)
=
λ
⋅
2
y
,
2
(
z
−
3
)
=
λ
⋅
2
z
.
2(x-2)=lambda*2x,quad2(y-6)=lambda*2y,quad2(z-3)=lambda*2z. 2(x – 2) = \lambda \cdot 2x, \quad 2(y – 6) = \lambda \cdot 2y, \quad 2(z – 3) = \lambda \cdot 2z. 2 ( x − 2 ) = λ ⋅ 2 x , 2 ( y − 6 ) = λ ⋅ 2 y , 2 ( z − 3 ) = λ ⋅ 2 z .
Simplify these equations:
x
−
2
=
λ
x
,
y
−
6
=
λ
y
,
z
−
3
=
λ
z
.
x
−
2
=
λ
x
,
y
−
6
=
λ
y
,
z
−
3
=
λ
z
.
x-2=lambda x,quad y-6=lambda y,quad z-3=lambda z. x – 2 = \lambda x, \quad y – 6 = \lambda y, \quad z – 3 = \lambda z. x − 2 = λ x , y − 6 = λ y , z − 3 = λ z .
Solve each for
λ
λ
lambda \lambda λ :
λ
=
x
−
2
x
,
λ
=
y
−
6
y
,
λ
=
z
−
3
z
.
λ
=
x
−
2
x
,
λ
=
y
−
6
y
,
λ
=
z
−
3
z
.
lambda=(x-2)/(x),quad lambda=(y-6)/(y),quad lambda=(z-3)/(z). \lambda = \frac{x – 2}{x}, \quad \lambda = \frac{y – 6}{y}, \quad \lambda = \frac{z – 3}{z}. λ = x − 2 x , λ = y − 6 y , λ = z − 3 z .
Since all expressions equal
λ
λ
lambda \lambda λ , set them equal to each other:
x
−
2
x
=
y
−
6
y
=
z
−
3
z
.
x
−
2
x
=
y
−
6
y
=
z
−
3
z
.
(x-2)/(x)=(y-6)/(y)=(z-3)/(z). \frac{x – 2}{x} = \frac{y – 6}{y} = \frac{z – 3}{z}. x − 2 x = y − 6 y = z − 3 z .
Step 4: Solve for
y
y
y y y and
z
z
z z z in Terms of
x
x
x x x
From
x
−
2
x
=
y
−
6
y
x
−
2
x
=
y
−
6
y
(x-2)/(x)=(y-6)/(y) \frac{x – 2}{x} = \frac{y – 6}{y} x − 2 x = y − 6 y :
x
y
−
2
y
=
x
y
−
6
x
⟹
−
2
y
=
−
6
x
⟹
y
=
3
x
.
x
y
−
2
y
=
x
y
−
6
x
⟹
−
2
y
=
−
6
x
⟹
y
=
3
x
.
xy-2y=xy-6xLongrightarrow-2y=-6xLongrightarrowy=3x. xy – 2y = xy – 6x \implies -2y = -6x \implies y = 3x. x y − 2 y = x y − 6 x ⟹ − 2 y = − 6 x ⟹ y = 3 x .
From
x
−
2
x
=
z
−
3
z
x
−
2
x
=
z
−
3
z
(x-2)/(x)=(z-3)/(z) \frac{x – 2}{x} = \frac{z – 3}{z} x − 2 x = z − 3 z :
x
z
−
2
z
=
x
z
−
3
x
⟹
−
2
z
=
−
3
x
⟹
z
=
3
2
x
.
x
z
−
2
z
=
x
z
−
3
x
⟹
−
2
z
=
−
3
x
⟹
z
=
3
2
x
.
xz-2z=xz-3xLongrightarrow-2z=-3xLongrightarrowz=(3)/(2)x. xz – 2z = xz – 3x \implies -2z = -3x \implies z = \frac{3}{2}x. x z − 2 z = x z − 3 x ⟹ − 2 z = − 3 x ⟹ z = 3 2 x .
Step 5: Substitute into the Sphere Equation
Substitute
y
=
3
x
y
=
3
x
y=3x y = 3x y = 3 x and
z
=
3
2
x
z
=
3
2
x
z=(3)/(2)x z = \frac{3}{2}x z = 3 2 x into
x
2
+
y
2
+
z
2
=
4
x
2
+
y
2
+
z
2
=
4
x^(2)+y^(2)+z^(2)=4 x^2 + y^2 + z^2 = 4 x 2 + y 2 + z 2 = 4 :
x
2
+
(
3
x
)
2
+
(
3
2
x
)
2
=
4
⟹
x
2
+
9
x
2
+
9
4
x
2
=
4.
x
2
+
(
3
x
)
2
+
3
2
x
2
=
4
⟹
x
2
+
9
x
2
+
9
4
x
2
=
4.
x^(2)+(3x)^(2)+((3)/(2)x)^(2)=4Longrightarrowx^(2)+9x^(2)+(9)/(4)x^(2)=4. x^2 + (3x)^2 + \left(\frac{3}{2}x\right)^2 = 4 \implies x^2 + 9x^2 + \frac{9}{4}x^2 = 4. x 2 + ( 3 x ) 2 + ( 3 2 x ) 2 = 4 ⟹ x 2 + 9 x 2 + 9 4 x 2 = 4.
Combine like terms:
(
1
+
9
+
9
4
)
x
2
=
4
⟹
49
4
x
2
=
4
⟹
x
2
=
16
49
⟹
x
=
±
4
7
.
1
+
9
+
9
4
x
2
=
4
⟹
49
4
x
2
=
4
⟹
x
2
=
16
49
⟹
x
=
±
4
7
.
(1+9+(9)/(4))x^(2)=4Longrightarrow(49)/(4)x^(2)=4Longrightarrowx^(2)=(16)/(49)Longrightarrowx=+-(4)/(7). \left(1 + 9 + \frac{9}{4}\right)x^2 = 4 \implies \frac{49}{4}x^2 = 4 \implies x^2 = \frac{16}{49} \implies x = \pm \frac{4}{7}. ( 1 + 9 + 9 4 ) x 2 = 4 ⟹ 49 4 x 2 = 4 ⟹ x 2 = 16 49 ⟹ x = ± 4 7 .
Step 6: Find Corresponding
y
y
y y y and
z
z
z z z
For
x
=
4
7
x
=
4
7
x=(4)/(7) x = \frac{4}{7} x = 4 7 :
y
=
3
⋅
4
7
=
12
7
,
z
=
3
2
⋅
4
7
=
6
7
.
y
=
3
⋅
4
7
=
12
7
,
z
=
3
2
⋅
4
7
=
6
7
.
y=3*(4)/(7)=(12)/(7),quad z=(3)/(2)*(4)/(7)=(6)/(7). y = 3 \cdot \frac{4}{7} = \frac{12}{7}, \quad z = \frac{3}{2} \cdot \frac{4}{7} = \frac{6}{7}. y = 3 ⋅ 4 7 = 12 7 , z = 3 2 ⋅ 4 7 = 6 7 .
For
x
=
−
4
7
x
=
−
4
7
x=-(4)/(7) x = -\frac{4}{7} x = − 4 7 :
y
=
3
⋅
(
−
4
7
)
=
−
12
7
,
z
=
3
2
⋅
(
−
4
7
)
=
−
6
7
.
y
=
3
⋅
−
4
7
=
−
12
7
,
z
=
3
2
⋅
−
4
7
=
−
6
7
.
y=3*(-(4)/(7))=-(12)/(7),quad z=(3)/(2)*(-(4)/(7))=-(6)/(7). y = 3 \cdot \left(-\frac{4}{7}\right) = -\frac{12}{7}, \quad z = \frac{3}{2} \cdot \left(-\frac{4}{7}\right) = -\frac{6}{7}. y = 3 ⋅ ( − 4 7 ) = − 12 7 , z = 3 2 ⋅ ( − 4 7 ) = − 6 7 .
Step 7: Compute the Distances
For
(
4
7
,
12
7
,
6
7
)
4
7
,
12
7
,
6
7
((4)/(7),(12)/(7),(6)/(7)) \left(\frac{4}{7}, \frac{12}{7}, \frac{6}{7}\right) ( 4 7 , 12 7 , 6 7 ) :
D
2
=
(
4
7
−
2
)
2
+
(
12
7
−
6
)
2
+
(
6
7
−
3
)
2
=
(
−
10
7
)
2
+
(
−
30
7
)
2
+
(
−
15
7
)
2
=
100
49
+
900
49
+
225
49
=
1225
49
=
25.
D
2
=
4
7
−
2
2
+
12
7
−
6
2
+
6
7
−
3
2
=
−
10
7
2
+
−
30
7
2
+
−
15
7
2
=
100
49
+
900
49
+
225
49
=
1225
49
=
25.
D^(2)=((4)/(7)-2)^(2)+((12)/(7)-6)^(2)+((6)/(7)-3)^(2)=(-(10)/(7))^(2)+(-(30)/(7))^(2)+(-(15)/(7))^(2)=(100)/(49)+(900)/(49)+(225)/(49)=(1225)/(49)=25. D^2 = \left(\frac{4}{7} – 2\right)^2 + \left(\frac{12}{7} – 6\right)^2 + \left(\frac{6}{7} – 3\right)^2 = \left(-\frac{10}{7}\right)^2 + \left(-\frac{30}{7}\right)^2 + \left(-\frac{15}{7}\right)^2 = \frac{100}{49} + \frac{900}{49} + \frac{225}{49} = \frac{1225}{49} = 25. D 2 = ( 4 7 − 2 ) 2 + ( 12 7 − 6 ) 2 + ( 6 7 − 3 ) 2 = ( − 10 7 ) 2 + ( − 30 7 ) 2 + ( − 15 7 ) 2 = 100 49 + 900 49 + 225 49 = 1225 49 = 25.
For
(
−
4
7
,
−
12
7
,
−
6
7
)
−
4
7
,
−
12
7
,
−
6
7
(-(4)/(7),-(12)/(7),-(6)/(7)) \left(-\frac{4}{7}, -\frac{12}{7}, -\frac{6}{7}\right) ( − 4 7 , − 12 7 , − 6 7 ) :
D
2
=
(
−
4
7
−
2
)
2
+
(
−
12
7
−
6
)
2
+
(
−
6
7
−
3
)
2
=
(
−
18
7
)
2
+
(
−
54
7
)
2
+
(
−
27
7
)
2
=
324
49
+
2916
49
+
729
49
=
3969
49
=
81.
D
2
=
−
4
7
−
2
2
+
−
12
7
−
6
2
+
−
6
7
−
3
2
=
−
18
7
2
+
−
54
7
2
+
−
27
7
2
=
324
49
+
2916
49
+
729
49
=
3969
49
=
81.
D^(2)=(-(4)/(7)-2)^(2)+(-(12)/(7)-6)^(2)+(-(6)/(7)-3)^(2)=(-(18)/(7))^(2)+(-(54)/(7))^(2)+(-(27)/(7))^(2)=(324)/(49)+(2916)/(49)+(729)/(49)=(3969)/(49)=81. D^2 = \left(-\frac{4}{7} – 2\right)^2 + \left(-\frac{12}{7} – 6\right)^2 + \left(-\frac{6}{7} – 3\right)^2 = \left(-\frac{18}{7}\right)^2 + \left(-\frac{54}{7}\right)^2 + \left(-\frac{27}{7}\right)^2 = \frac{324}{49} + \frac{2916}{49} + \frac{729}{49} = \frac{3969}{49} = 81. D 2 = ( − 4 7 − 2 ) 2 + ( − 12 7 − 6 ) 2 + ( − 6 7 − 3 ) 2 = ( − 18 7 ) 2 + ( − 54 7 ) 2 + ( − 27 7 ) 2 = 324 49 + 2916 49 + 729 49 = 3969 49 = 81.
Step 8: Determine Minimum and Maximum Distances
Minimum distance:
D
=
25
=
5
D
=
25
=
5
D=sqrt25=5 D = \sqrt{25} = 5 D = 25 = 5 .
Maximum distance:
D
=
81
=
9
D
=
81
=
9
D=sqrt81=9 D = \sqrt{81} = 9 D = 81 = 9 .
Final Answer
Minimum distance:
5
,
Maximum distance:
9
Minimum distance:
5
,
Maximum distance:
9
“Minimum distance: “5,” Maximum distance: “9 \boxed{\text{Minimum distance: } 5, \text{ Maximum distance: } 9} Minimum distance: 5 , Maximum distance: 9
Question:-02 (c)
Evaluate
∫
0
2
π
cos
2
θ
5
+
4
cos
θ
d
θ
∫
0
2
π
cos
2
θ
5
+
4
cos
θ
d
θ
int_(0)^(2pi)(cos 2theta)/(5+4cos theta)d theta \int_0^{2\pi} \frac{\cos 2\theta}{5 + 4 \cos \theta} d\theta ∫ 0 2 π cos 2 θ 5 + 4 cos θ d θ using contour integration.
Answer:
To evaluate the integral
I
=
∫
0
2
π
cos
2
θ
5
+
4
cos
θ
d
θ
I
=
∫
0
2
π
cos
2
θ
5
+
4
cos
θ
d
θ
I=int_(0)^(2pi)(cos 2theta)/(5+4cos theta)d theta I = \int_0^{2\pi} \frac{\cos 2\theta}{5 + 4 \cos \theta} \, d\theta I = ∫ 0 2 π cos 2 θ 5 + 4 cos θ d θ
using contour integration , we proceed with the following steps:
Step 1: Parameterize the Integral Using
z
=
e
i
θ
z
=
e
i
θ
z=e^(i theta) z = e^{i\theta} z = e i θ
Let
z
=
e
i
θ
z
=
e
i
θ
z=e^(i theta) z = e^{i\theta} z = e i θ , so that
d
θ
=
d
z
i
z
d
θ
=
d
z
i
z
d theta=(dz)/(iz) d\theta = \frac{dz}{iz} d θ = d z i z . The integral becomes a contour integral over the unit circle
|
z
|
=
1
|
z
|
=
1
|z|=1 |z| = 1 | z | = 1 :
cos
θ
=
z
+
z
−
1
2
,
cos
2
θ
=
z
2
+
z
−
2
2
.
cos
θ
=
z
+
z
−
1
2
,
cos
2
θ
=
z
2
+
z
−
2
2
.
cos theta=(z+z^(-1))/(2),quad cos 2theta=(z^(2)+z^(-2))/(2). \cos \theta = \frac{z + z^{-1}}{2}, \quad \cos 2\theta = \frac{z^2 + z^{-2}}{2}. cos θ = z + z − 1 2 , cos 2 θ = z 2 + z − 2 2 .
Substituting these into the integral:
I
=
∮
|
z
|
=
1
z
2
+
z
−
2
2
5
+
4
(
z
+
z
−
1
2
)
⋅
d
z
i
z
.
I
=
∮
|
z
|
=
1
z
2
+
z
−
2
2
5
+
4
z
+
z
−
1
2
⋅
d
z
i
z
.
I=oint_(|z|=1)((z^(2)+z^(-2))/(2))/(5+4((z+z^(-1))/(2)))*(dz)/(iz). I = \oint_{|z|=1} \frac{\frac{z^2 + z^{-2}}{2}}{5 + 4 \left( \frac{z + z^{-1}}{2} \right)} \cdot \frac{dz}{iz}. I = ∮ | z | = 1 z 2 + z − 2 2 5 + 4 ( z + z − 1 2 ) ⋅ d z i z .
Simplify the integrand:
I
=
1
2
i
∮
|
z
|
=
1
z
2
+
z
−
2
5
+
2
(
z
+
z
−
1
)
⋅
d
z
z
=
1
2
i
∮
|
z
|
=
1
z
4
+
1
z
2
(
2
z
2
+
5
z
+
2
)
d
z
.
I
=
1
2
i
∮
|
z
|
=
1
z
2
+
z
−
2
5
+
2
(
z
+
z
−
1
)
⋅
d
z
z
=
1
2
i
∮
|
z
|
=
1
z
4
+
1
z
2
(
2
z
2
+
5
z
+
2
)
d
z
.
I=(1)/(2i)oint_(|z|=1)(z^(2)+z^(-2))/(5+2(z+z^(-1)))*(dz)/(z)=(1)/(2i)oint_(|z|=1)(z^(4)+1)/(z^(2)(2z^(2)+5z+2))dz. I = \frac{1}{2i} \oint_{|z|=1} \frac{z^2 + z^{-2}}{5 + 2(z + z^{-1})} \cdot \frac{dz}{z} = \frac{1}{2i} \oint_{|z|=1} \frac{z^4 + 1}{z^2 (2z^2 + 5z + 2)} \, dz. I = 1 2 i ∮ | z | = 1 z 2 + z − 2 5 + 2 ( z + z − 1 ) ⋅ d z z = 1 2 i ∮ | z | = 1 z 4 + 1 z 2 ( 2 z 2 + 5 z + 2 ) d z .
Step 2: Factor the Denominator
The denominator
2
z
2
+
5
z
+
2
2
z
2
+
5
z
+
2
2z^(2)+5z+2 2z^2 + 5z + 2 2 z 2 + 5 z + 2 factors as:
2
z
2
+
5
z
+
2
=
(
2
z
+
1
)
(
z
+
2
)
.
2
z
2
+
5
z
+
2
=
(
2
z
+
1
)
(
z
+
2
)
.
2z^(2)+5z+2=(2z+1)(z+2). 2z^2 + 5z + 2 = (2z + 1)(z + 2). 2 z 2 + 5 z + 2 = ( 2 z + 1 ) ( z + 2 ) .
Thus, the integrand becomes:
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
.
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
.
(z^(4)+1)/(z^(2)(2z+1)(z+2)). \frac{z^4 + 1}{z^2 (2z + 1)(z + 2)}. z 4 + 1 z 2 ( 2 z + 1 ) ( z + 2 ) .
Step 3: Identify Poles Inside the Unit Circle
The poles are at:
z
=
0
z
=
0
z=0 z = 0 z = 0 (order 2),
z
=
−
1
2
z
=
−
1
2
z=-(1)/(2) z = -\frac{1}{2} z = − 1 2 (from
2
z
+
1
=
0
2
z
+
1
=
0
2z+1=0 2z + 1 = 0 2 z + 1 = 0 ),
z
=
−
2
z
=
−
2
z=-2 z = -2 z = − 2 (from
z
+
2
=
0
z
+
2
=
0
z+2=0 z + 2 = 0 z + 2 = 0 ).
Only
z
=
0
z
=
0
z=0 z = 0 z = 0 and
z
=
−
1
2
z
=
−
1
2
z=-(1)/(2) z = -\frac{1}{2} z = − 1 2 lie inside the unit circle
|
z
|
=
1
|
z
|
=
1
|z|=1 |z| = 1 | z | = 1 .
Step 4: Compute Residues
Residue at
z
=
0
z
=
0
z=0 z = 0 z = 0 :
The integrand has a double pole at
z
=
0
z
=
0
z=0 z = 0 z = 0 . To find the residue, compute the coefficient of
1
z
1
z
(1)/(z) \frac{1}{z} 1 z in the Laurent expansion:
Res
(
f
,
0
)
=
lim
z
→
0
d
d
z
(
z
2
⋅
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
)
=
lim
z
→
0
d
d
z
(
z
4
+
1
(
2
z
+
1
)
(
z
+
2
)
)
.
Res
(
f
,
0
)
=
lim
z
→
0
d
d
z
z
2
⋅
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
=
lim
z
→
0
d
d
z
z
4
+
1
(
2
z
+
1
)
(
z
+
2
)
.
“Res”(f,0)=lim_(z rarr0)(d)/(dz)(z^(2)*(z^(4)+1)/(z^(2)(2z+1)(z+2)))=lim_(z rarr0)(d)/(dz)((z^(4)+1)/((2z+1)(z+2))). \text{Res}(f, 0) = \lim_{z \to 0} \frac{d}{dz} \left( z^2 \cdot \frac{z^4 + 1}{z^2 (2z + 1)(z + 2)} \right) = \lim_{z \to 0} \frac{d}{dz} \left( \frac{z^4 + 1}{(2z + 1)(z + 2)} \right). Res ( f , 0 ) = lim z → 0 d d z ( z 2 ⋅ z 4 + 1 z 2 ( 2 z + 1 ) ( z + 2 ) ) = lim z → 0 d d z ( z 4 + 1 ( 2 z + 1 ) ( z + 2 ) ) .
Compute the derivative:
d
d
z
(
z
4
+
1
(
2
z
+
1
)
(
z
+
2
)
)
=
4
z
3
(
2
z
+
1
)
(
z
+
2
)
−
(
z
4
+
1
)
(
2
(
z
+
2
)
+
(
2
z
+
1
)
)
(
2
z
+
1
)
2
(
z
+
2
)
2
.
d
d
z
z
4
+
1
(
2
z
+
1
)
(
z
+
2
)
=
4
z
3
(
2
z
+
1
)
(
z
+
2
)
−
(
z
4
+
1
)
(
2
(
z
+
2
)
+
(
2
z
+
1
)
)
(
2
z
+
1
)
2
(
z
+
2
)
2
.
(d)/(dz)((z^(4)+1)/((2z+1)(z+2)))=(4z^(3)(2z+1)(z+2)-(z^(4)+1)(2(z+2)+(2z+1)))/((2z+1)^(2)(z+2)^(2)). \frac{d}{dz} \left( \frac{z^4 + 1}{(2z + 1)(z + 2)} \right) = \frac{4z^3 (2z + 1)(z + 2) – (z^4 + 1)(2(z + 2) + (2z + 1))}{(2z + 1)^2 (z + 2)^2}. d d z ( z 4 + 1 ( 2 z + 1 ) ( z + 2 ) ) = 4 z 3 ( 2 z + 1 ) ( z + 2 ) − ( z 4 + 1 ) ( 2 ( z + 2 ) + ( 2 z + 1 ) ) ( 2 z + 1 ) 2 ( z + 2 ) 2 .
Evaluating at
z
=
0
z
=
0
z=0 z = 0 z = 0 :
Res
(
f
,
0
)
=
0
−
1
⋅
(
4
+
1
)
1
⋅
4
=
−
5
4
.
Res
(
f
,
0
)
=
0
−
1
⋅
(
4
+
1
)
1
⋅
4
=
−
5
4
.
“Res”(f,0)=(0-1*(4+1))/(1*4)=-(5)/(4). \text{Res}(f, 0) = \frac{0 – 1 \cdot (4 + 1)}{1 \cdot 4} = -\frac{5}{4}. Res ( f , 0 ) = 0 − 1 ⋅ ( 4 + 1 ) 1 ⋅ 4 = − 5 4 .
Residue at
z
=
−
1
2
z
=
−
1
2
z=-(1)/(2) z = -\frac{1}{2} z = − 1 2 :
The integrand has a simple pole at
z
=
−
1
2
z
=
−
1
2
z=-(1)/(2) z = -\frac{1}{2} z = − 1 2 . The residue is:
Res
(
f
,
−
1
2
)
=
lim
z
→
−
1
2
(
z
+
1
2
)
⋅
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
=
(
−
1
2
)
4
+
1
(
−
1
2
)
2
⋅
2
⋅
(
−
1
2
+
2
)
=
1
16
+
1
1
4
⋅
2
⋅
3
2
=
17
16
3
4
=
17
12
.
Res
(
f
,
−
1
2
)
=
lim
z
→
−
1
2
z
+
1
2
⋅
z
4
+
1
z
2
(
2
z
+
1
)
(
z
+
2
)
=
−
1
2
4
+
1
−
1
2
2
⋅
2
⋅
−
1
2
+
2
=
1
16
+
1
1
4
⋅
2
⋅
3
2
=
17
16
3
4
=
17
12
.
“Res”(f,-(1)/(2))=lim_(z rarr-(1)/(2))(z+(1)/(2))*(z^(4)+1)/(z^(2)(2z+1)(z+2))=((-(1)/(2))^(4)+1)/((-(1)/(2))^(2)*2*(-(1)/(2)+2))=((1)/(16)+1)/((1)/(4)*2*(3)/(2))=((17)/(16))/((3)/(4))=(17)/(12). \text{Res}(f, -\frac{1}{2}) = \lim_{z \to -\frac{1}{2}} \left( z + \frac{1}{2} \right) \cdot \frac{z^4 + 1}{z^2 (2z + 1)(z + 2)} = \frac{\left(-\frac{1}{2}\right)^4 + 1}{\left(-\frac{1}{2}\right)^2 \cdot 2 \cdot \left(-\frac{1}{2} + 2\right)} = \frac{\frac{1}{16} + 1}{\frac{1}{4} \cdot 2 \cdot \frac{3}{2}} = \frac{\frac{17}{16}}{\frac{3}{4}} = \frac{17}{12}. Res ( f , − 1 2 ) = lim z → − 1 2 ( z + 1 2 ) ⋅ z 4 + 1 z 2 ( 2 z + 1 ) ( z + 2 ) = ( − 1 2 ) 4 + 1 ( − 1 2 ) 2 ⋅ 2 ⋅ ( − 1 2 + 2 ) = 1 16 + 1 1 4 ⋅ 2 ⋅ 3 2 = 17 16 3 4 = 17 12 .
Step 5: Apply the Residue Theorem
The integral is
2
π
i
2
π
i
2pi i 2\pi i 2 π i times the sum of the residues inside the contour:
I
=
1
2
i
⋅
2
π
i
(
Res
(
f
,
0
)
+
Res
(
f
,
−
1
2
)
)
=
π
(
−
5
4
+
17
12
)
=
π
(
−
15
+
17
12
)
=
π
⋅
2
12
=
π
6
.
I
=
1
2
i
⋅
2
π
i
Res
(
f
,
0
)
+
Res
(
f
,
−
1
2
)
=
π
−
5
4
+
17
12
=
π
−
15
+
17
12
=
π
⋅
2
12
=
π
6
.
I=(1)/(2i)*2pi i(“Res”(f,0)+”Res”(f,-(1)/(2)))=pi(-(5)/(4)+(17)/(12))=pi((-15+17)/(12))=pi*(2)/(12)=(pi)/(6). I = \frac{1}{2i} \cdot 2\pi i \left( \text{Res}(f, 0) + \text{Res}(f, -\frac{1}{2}) \right) = \pi \left( -\frac{5}{4} + \frac{17}{12} \right) = \pi \left( \frac{-15 + 17}{12} \right) = \pi \cdot \frac{2}{12} = \frac{\pi}{6}. I = 1 2 i ⋅ 2 π i ( Res ( f , 0 ) + Res ( f , − 1 2 ) ) = π ( − 5 4 + 17 12 ) = π ( − 15 + 17 12 ) = π ⋅ 2 12 = π 6 .
Final Answer
π
6
π
6
(pi)/(6) \boxed{\frac{\pi}{6}} π 6
Question:-03
(a) Prove that
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is an irreducible polynomial in
Z
3
[
x
]
Z
3
[
x
]
Z_(3)[x] Z_3[x] Z 3 [ x ] . Further show that the quotient ring
Z
3
[
x
]
⟨
x
2
+
1
⟩
Z
3
[
x
]
⟨
x
2
+
1
⟩
(Z_(3)[x])/((:x^(2)+1:)) \frac{Z_3[x]}{\langle x^2 + 1 \rangle} Z 3 [ x ] ⟨ x 2 + 1 ⟩ is a field of 9 elements.
Answer:
Proof that
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is Irreducible in
Z
3
[
x
]
Z
3
[
x
]
Z_(3)[x] \mathbb{Z}_3[x] Z 3 [ x ]
A polynomial
f
(
x
)
∈
Z
3
[
x
]
f
(
x
)
∈
Z
3
[
x
]
f(x)inZ_(3)[x] f(x) \in \mathbb{Z}_3[x] f ( x ) ∈ Z 3 [ x ] is
irreducible if it cannot be factored into a product of two non-constant polynomials in
Z
3
[
x
]
Z
3
[
x
]
Z_(3)[x] \mathbb{Z}_3[x] Z 3 [ x ] .
Step 1: Check for Roots in
Z
3
Z
3
Z_(3) \mathbb{Z}_3 Z 3
A quadratic polynomial is irreducible over a field if it has no roots in that field. Evaluate
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 at all elements of
Z
3
=
{
0
,
1
,
2
}
Z
3
=
{
0
,
1
,
2
}
Z_(3)={0,1,2} \mathbb{Z}_3 = \{0, 1, 2\} Z 3 = { 0 , 1 , 2 } :
At
x
=
0
x
=
0
x=0 x = 0 x = 0 :
0
2
+
1
=
1
≠
0
0
2
+
1
=
1
≠
0
0^(2)+1=1!=0 0^2 + 1 = 1 \neq 0 0 2 + 1 = 1 ≠ 0 ,
At
x
=
1
x
=
1
x=1 x = 1 x = 1 :
1
2
+
1
=
2
≠
0
1
2
+
1
=
2
≠
0
1^(2)+1=2!=0 1^2 + 1 = 2 \neq 0 1 2 + 1 = 2 ≠ 0 ,
At
x
=
2
x
=
2
x=2 x = 2 x = 2 :
2
2
+
1
=
4
≡
1
≠
0
2
2
+
1
=
4
≡
1
≠
0
2^(2)+1=4-=1!=0 2^2 + 1 = 4 \equiv 1 \neq 0 2 2 + 1 = 4 ≡ 1 ≠ 0 .
Since
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 has no roots in
Z
3
Z
3
Z_(3) \mathbb{Z}_3 Z 3 , it cannot be factored into linear polynomials, and thus it is irreducible.
Step 2: Confirm No Factorization into Quadratics
Since
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is quadratic, the only possible non-trivial factorization would be into two linear polynomials. Since no such factorization exists,
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is irreducible.
Proof that
Z
3
[
x
]
⟨
x
2
+
1
⟩
Z
3
[
x
]
⟨
x
2
+
1
⟩
(Z_(3)[x])/((:x^(2)+1:)) \frac{\mathbb{Z}_3[x]}{\langle x^2 + 1 \rangle} Z 3 [ x ] ⟨ x 2 + 1 ⟩ is a Field of 9 Elements
Step 1: Structure of the Quotient Ring
The quotient ring
Z
3
[
x
]
⟨
x
2
+
1
⟩
Z
3
[
x
]
⟨
x
2
+
1
⟩
(Z_(3)[x])/((:x^(2)+1:)) \frac{\mathbb{Z}_3[x]}{\langle x^2 + 1 \rangle} Z 3 [ x ] ⟨ x 2 + 1 ⟩ consists of all polynomials in
Z
3
[
x
]
Z
3
[
x
]
Z_(3)[x] \mathbb{Z}_3[x] Z 3 [ x ] modulo
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 . Since
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is irreducible, the ideal
⟨
x
2
+
1
⟩
⟨
x
2
+
1
⟩
(:x^(2)+1:) \langle x^2 + 1 \rangle ⟨ x 2 + 1 ⟩ is maximal, and thus the quotient ring is a
field .
Step 2: Elements of the Quotient Field
Every element in
Z
3
[
x
]
⟨
x
2
+
1
⟩
Z
3
[
x
]
⟨
x
2
+
1
⟩
(Z_(3)[x])/((:x^(2)+1:)) \frac{\mathbb{Z}_3[x]}{\langle x^2 + 1 \rangle} Z 3 [ x ] ⟨ x 2 + 1 ⟩ can be represented uniquely as a linear polynomial:
a
+
b
x
where
a
,
b
∈
Z
3
.
a
+
b
x
where
a
,
b
∈
Z
3
.
a+bx quad”where”quad a,b inZ_(3). a + bx \quad \text{where} \quad a, b \in \mathbb{Z}_3. a + b x where a , b ∈ Z 3 .
Since there are 3 choices for
a
a
a a a and 3 choices for
b
b
b b b , the total number of distinct elements is
3
×
3
=
9
3
×
3
=
9
3xx3=9 3 \times 3 = 9 3 × 3 = 9 .
Step 3: Verification of Field Axioms
Addition and Multiplication are performed modulo
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 , with
x
2
≡
−
1
≡
2
x
2
≡
−
1
≡
2
x^(2)-=-1-=2 x^2 \equiv -1 \equiv 2 x 2 ≡ − 1 ≡ 2 .
Inverses : Every non-zero element
a
+
b
x
a
+
b
x
a+bx a + bx a + b x has a multiplicative inverse because
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is irreducible. For example:
The inverse of
1
+
x
1
+
x
1+x 1 + x 1 + x is found by solving
(
1
+
x
)
(
c
+
d
x
)
≡
1
mod
(
x
2
+
1
)
(
1
+
x
)
(
c
+
d
x
)
≡
1
mod
(
x
2
+
1
)
(1+x)(c+dx)-=1mod(x^(2)+1) (1 + x)(c + dx) \equiv 1 \mod (x^2 + 1) ( 1 + x ) ( c + d x ) ≡ 1 mod ( x 2 + 1 ) , leading to
c
+
d
=
1
c
+
d
=
1
c+d=1 c + d = 1 c + d = 1 and
c
−
d
=
0
c
−
d
=
0
c-d=0 c – d = 0 c − d = 0 , so
c
=
d
=
2
c
=
d
=
2
c=d=2 c = d = 2 c = d = 2 . Thus,
(
1
+
x
)
−
1
=
2
+
2
x
(
1
+
x
)
−
1
=
2
+
2
x
(1+x)^(-1)=2+2x (1 + x)^{-1} = 2 + 2x ( 1 + x ) − 1 = 2 + 2 x .
Conclusion
x
2
+
1
x
2
+
1
x^(2)+1 x^2 + 1 x 2 + 1 is irreducible in
Z
3
[
x
]
Z
3
[
x
]
Z_(3)[x] \mathbb{Z}_3[x] Z 3 [ x ] because it has no roots in
Z
3
Z
3
Z_(3) \mathbb{Z}_3 Z 3 .
The quotient ring
Z
3
[
x
]
⟨
x
2
+
1
⟩
Z
3
[
x
]
⟨
x
2
+
1
⟩
(Z_(3)[x])/((:x^(2)+1:)) \frac{\mathbb{Z}_3[x]}{\langle x^2 + 1 \rangle} Z 3 [ x ] ⟨ x 2 + 1 ⟩ is a field with 9 elements , as it satisfies all field axioms and has the correct cardinality.
Question:-03 (b)
Prove that
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u(x,y)=e^(x)(x cos y-y sin y) u(x, y) = e^x (x \cos y – y \sin y) u ( x , y ) = e x ( x cos y − y sin y ) is harmonic. Find its conjugate harmonic function
v
(
x
,
y
)
v
(
x
,
y
)
v(x,y) v(x, y) v ( x , y ) and express the corresponding analytic function
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) in terms of
z
z
z z z .
Answer:
Step 1: Verify that
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u(x,y)=e^(x)(x cos y-y sin y) u(x, y) = e^x (x \cos y – y \sin y) u ( x , y ) = e x ( x cos y − y sin y ) is Harmonic
A function
u
(
x
,
y
)
u
(
x
,
y
)
u(x,y) u(x, y) u ( x , y ) is
harmonic if it satisfies
Laplace’s equation :
∂
2
u
∂
x
2
+
∂
2
u
∂
y
2
=
0.
∂
2
u
∂
x
2
+
∂
2
u
∂
y
2
=
0.
(del^(2)u)/(delx^(2))+(del^(2)u)/(dely^(2))=0. \frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = 0. ∂ 2 u ∂ x 2 + ∂ 2 u ∂ y 2 = 0.
Compute the First Partial Derivatives:
∂
u
∂
x
=
e
x
(
x
cos
y
−
y
sin
y
)
+
e
x
cos
y
=
e
x
(
(
x
+
1
)
cos
y
−
y
sin
y
)
,
∂
u
∂
x
=
e
x
(
x
cos
y
−
y
sin
y
)
+
e
x
cos
y
=
e
x
(
x
+
1
)
cos
y
−
y
sin
y
,
(del u)/(del x)=e^(x)(x cos y-y sin y)+e^(x)cos y=e^(x)((x+1)cos y-y sin y), \frac{\partial u}{\partial x} = e^x (x \cos y – y \sin y) + e^x \cos y = e^x \left( (x + 1) \cos y – y \sin y \right), ∂ u ∂ x = e x ( x cos y − y sin y ) + e x cos y = e x ( ( x + 1 ) cos y − y sin y ) ,
∂
u
∂
y
=
e
x
(
−
x
sin
y
−
sin
y
−
y
cos
y
)
=
−
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
∂
u
∂
y
=
e
x
(
−
x
sin
y
−
sin
y
−
y
cos
y
)
=
−
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
(del u)/(del y)=e^(x)(-x sin y-sin y-y cos y)=-e^(x)((x+1)sin y+y cos y). \frac{\partial u}{\partial y} = e^x (-x \sin y – \sin y – y \cos y) = -e^x \left( (x + 1) \sin y + y \cos y \right). ∂ u ∂ y = e x ( − x sin y − sin y − y cos y ) = − e x ( ( x + 1 ) sin y + y cos y ) .
Compute the Second Partial Derivatives:
∂
2
u
∂
x
2
=
∂
∂
x
(
e
x
(
(
x
+
1
)
cos
y
−
y
sin
y
)
)
=
e
x
(
(
x
+
2
)
cos
y
−
y
sin
y
)
,
∂
2
u
∂
x
2
=
∂
∂
x
e
x
(
x
+
1
)
cos
y
−
y
sin
y
=
e
x
(
x
+
2
)
cos
y
−
y
sin
y
,
(del^(2)u)/(delx^(2))=(del)/(del x)(e^(x)((x+1)cos y-y sin y))=e^(x)((x+2)cos y-y sin y), \frac{\partial^2 u}{\partial x^2} = \frac{\partial}{\partial x} \left( e^x \left( (x + 1) \cos y – y \sin y \right) \right) = e^x \left( (x + 2) \cos y – y \sin y \right), ∂ 2 u ∂ x 2 = ∂ ∂ x ( e x ( ( x + 1 ) cos y − y sin y ) ) = e x ( ( x + 2 ) cos y − y sin y ) ,
∂
2
u
∂
y
2
=
∂
∂
y
(
−
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
)
=
−
e
x
(
(
x
+
1
)
cos
y
+
cos
y
−
y
sin
y
)
=
−
e
x
(
(
x
+
2
)
cos
y
−
y
sin
y
)
.
∂
2
u
∂
y
2
=
∂
∂
y
−
e
x
(
x
+
1
)
sin
y
+
y
cos
y
=
−
e
x
(
x
+
1
)
cos
y
+
cos
y
−
y
sin
y
=
−
e
x
(
x
+
2
)
cos
y
−
y
sin
y
.
(del^(2)u)/(dely^(2))=(del)/(del y)(-e^(x)((x+1)sin y+y cos y))=-e^(x)((x+1)cos y+cos y-y sin y)=-e^(x)((x+2)cos y-y sin y). \frac{\partial^2 u}{\partial y^2} = \frac{\partial}{\partial y} \left( -e^x \left( (x + 1) \sin y + y \cos y \right) \right) = -e^x \left( (x + 1) \cos y + \cos y – y \sin y \right) = -e^x \left( (x + 2) \cos y – y \sin y \right). ∂ 2 u ∂ y 2 = ∂ ∂ y ( − e x ( ( x + 1 ) sin y + y cos y ) ) = − e x ( ( x + 1 ) cos y + cos y − y sin y ) = − e x ( ( x + 2 ) cos y − y sin y ) .
Check Laplace’s Equation:
∂
2
u
∂
x
2
+
∂
2
u
∂
y
2
=
e
x
(
(
x
+
2
)
cos
y
−
y
sin
y
)
−
e
x
(
(
x
+
2
)
cos
y
−
y
sin
y
)
=
0.
∂
2
u
∂
x
2
+
∂
2
u
∂
y
2
=
e
x
(
x
+
2
)
cos
y
−
y
sin
y
−
e
x
(
x
+
2
)
cos
y
−
y
sin
y
=
0.
(del^(2)u)/(delx^(2))+(del^(2)u)/(dely^(2))=e^(x)((x+2)cos y-y sin y)-e^(x)((x+2)cos y-y sin y)=0. \frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = e^x \left( (x + 2) \cos y – y \sin y \right) – e^x \left( (x + 2) \cos y – y \sin y \right) = 0. ∂ 2 u ∂ x 2 + ∂ 2 u ∂ y 2 = e x ( ( x + 2 ) cos y − y sin y ) − e x ( ( x + 2 ) cos y − y sin y ) = 0.
Thus,
u
(
x
,
y
)
u
(
x
,
y
)
u(x,y) u(x, y) u ( x , y ) is
harmonic .
Step 2: Find the Conjugate Harmonic Function
v
(
x
,
y
)
v
(
x
,
y
)
v(x,y) v(x, y) v ( x , y )
Since
u
(
x
,
y
)
u
(
x
,
y
)
u(x,y) u(x, y) u ( x , y ) is harmonic, there exists a
conjugate harmonic function
v
(
x
,
y
)
v
(
x
,
y
)
v(x,y) v(x, y) v ( x , y ) such that
f
(
z
)
=
u
+
i
v
f
(
z
)
=
u
+
i
v
f(z)=u+iv f(z) = u + iv f ( z ) = u + i v is analytic. To find
v
v
v v v , we use the
Cauchy-Riemann equations :
∂
u
∂
x
=
∂
v
∂
y
,
∂
u
∂
y
=
−
∂
v
∂
x
.
∂
u
∂
x
=
∂
v
∂
y
,
∂
u
∂
y
=
−
∂
v
∂
x
.
(del u)/(del x)=(del v)/(del y),quad(del u)/(del y)=-(del v)/(del x). \frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \quad \frac{\partial u}{\partial y} = -\frac{\partial v}{\partial x}. ∂ u ∂ x = ∂ v ∂ y , ∂ u ∂ y = − ∂ v ∂ x .
From
∂
u
∂
x
=
∂
v
∂
y
∂
u
∂
x
=
∂
v
∂
y
(del u)/(del x)=(del v)/(del y) \frac{\partial u}{\partial x} = \frac{\partial v}{\partial y} ∂ u ∂ x = ∂ v ∂ y :
∂
v
∂
y
=
e
x
(
(
x
+
1
)
cos
y
−
y
sin
y
)
.
∂
v
∂
y
=
e
x
(
x
+
1
)
cos
y
−
y
sin
y
.
(del v)/(del y)=e^(x)((x+1)cos y-y sin y). \frac{\partial v}{\partial y} = e^x \left( (x + 1) \cos y – y \sin y \right). ∂ v ∂ y = e x ( ( x + 1 ) cos y − y sin y ) .
Integrate with respect to
y
y
y y y :
v
(
x
,
y
)
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
+
g
(
x
)
,
v
(
x
,
y
)
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
+
g
(
x
)
,
v(x,y)=e^(x)((x+1)sin y+y cos y)+g(x), v(x, y) = e^x \left( (x + 1) \sin y + y \cos y \right) + g(x), v ( x , y ) = e x ( ( x + 1 ) sin y + y cos y ) + g ( x ) ,
where
g
(
x
)
g
(
x
)
g(x) g(x) g ( x ) is an arbitrary function of
x
x
x x x .
From
∂
u
∂
y
=
−
∂
v
∂
x
∂
u
∂
y
=
−
∂
v
∂
x
(del u)/(del y)=-(del v)/(del x) \frac{\partial u}{\partial y} = -\frac{\partial v}{\partial x} ∂ u ∂ y = − ∂ v ∂ x :
∂
v
∂
x
=
−
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
∂
v
∂
x
=
−
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
(del v)/(del x)=-e^(x)((x+1)sin y+y cos y). \frac{\partial v}{\partial x} = -e^x \left( (x + 1) \sin y + y \cos y \right). ∂ v ∂ x = − e x ( ( x + 1 ) sin y + y cos y ) .
Differentiate
v
(
x
,
y
)
v
(
x
,
y
)
v(x,y) v(x, y) v ( x , y ) with respect to
x
x
x x x :
∂
v
∂
x
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
+
e
x
sin
y
+
g
′
(
x
)
.
∂
v
∂
x
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
+
e
x
sin
y
+
g
′
(
x
)
.
(del v)/(del x)=e^(x)((x+1)sin y+y cos y)+e^(x)sin y+g^(‘)(x). \frac{\partial v}{\partial x} = e^x \left( (x + 1) \sin y + y \cos y \right) + e^x \sin y + g'(x). ∂ v ∂ x = e x ( ( x + 1 ) sin y + y cos y ) + e x sin y + g ′ ( x ) .
Set this equal to
−
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
−
e
x
(
x
+
1
)
sin
y
+
y
cos
y
-e^(x)((x+1)sin y+y cos y) -e^x \left( (x + 1) \sin y + y \cos y \right) − e x ( ( x + 1 ) sin y + y cos y ) :
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
+
e
x
sin
y
+
g
′
(
x
)
=
−
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
e
x
(
x
+
1
)
sin
y
+
y
cos
y
+
e
x
sin
y
+
g
′
(
x
)
=
−
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
e^(x)((x+1)sin y+y cos y)+e^(x)sin y+g^(‘)(x)=-e^(x)((x+1)sin y+y cos y). e^x \left( (x + 1) \sin y + y \cos y \right) + e^x \sin y + g'(x) = -e^x \left( (x + 1) \sin y + y \cos y \right). e x ( ( x + 1 ) sin y + y cos y ) + e x sin y + g ′ ( x ) = − e x ( ( x + 1 ) sin y + y cos y ) .
Simplify:
2
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
+
e
x
sin
y
+
g
′
(
x
)
=
0.
2
e
x
(
x
+
1
)
sin
y
+
y
cos
y
+
e
x
sin
y
+
g
′
(
x
)
=
0.
2e^(x)((x+1)sin y+y cos y)+e^(x)sin y+g^(‘)(x)=0. 2e^x \left( (x + 1) \sin y + y \cos y \right) + e^x \sin y + g'(x) = 0. 2 e x ( ( x + 1 ) sin y + y cos y ) + e x sin y + g ′ ( x ) = 0.
This must hold for all
x
x
x x x and
y
y
y y y , so:
g
′
(
x
)
=
0
⟹
g
(
x
)
=
C
(a constant)
.
g
′
(
x
)
=
0
⟹
g
(
x
)
=
C
(a constant)
.
g^(‘)(x)=0Longrightarrowg(x)=C quad(a constant). g'(x) = 0 \implies g(x) = C \quad \text{(a constant)}. g ′ ( x ) = 0 ⟹ g ( x ) = C (a constant) .
Thus, the conjugate harmonic function is:
v
(
x
,
y
)
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
+
C
.
v
(
x
,
y
)
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
+
C
.
v(x,y)=e^(x)((x+1)sin y+y cos y)+C. v(x, y) = e^x \left( (x + 1) \sin y + y \cos y \right) + C. v ( x , y ) = e x ( ( x + 1 ) sin y + y cos y ) + C .
For simplicity, we can take
C
=
0
C
=
0
C=0 C = 0 C = 0 :
v
(
x
,
y
)
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
v
(
x
,
y
)
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
v(x,y)=e^(x)((x+1)sin y+y cos y). v(x, y) = e^x \left( (x + 1) \sin y + y \cos y \right). v ( x , y ) = e x ( ( x + 1 ) sin y + y cos y ) .
Step 3: Express the Analytic Function
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) in Terms of
z
z
z z z
The analytic function is:
f
(
z
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
+
i
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
f
(
z
)
=
u
(
x
,
y
)
+
i
v
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
+
i
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
f(z)=u(x,y)+iv(x,y)=e^(x)(x cos y-y sin y)+ie^(x)((x+1)sin y+y cos y). f(z) = u(x, y) + iv(x, y) = e^x (x \cos y – y \sin y) + i e^x \left( (x + 1) \sin y + y \cos y \right). f ( z ) = u ( x , y ) + i v ( x , y ) = e x ( x cos y − y sin y ) + i e x ( ( x + 1 ) sin y + y cos y ) .
To express
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) in terms of
z
=
x
+
i
y
z
=
x
+
i
y
z=x+iy z = x + iy z = x + i y , we observe that:
f
(
z
)
=
e
x
(
x
(
cos
y
+
i
sin
y
)
+
i
y
(
cos
y
+
i
sin
y
)
+
i
sin
y
)
=
e
x
(
(
x
+
i
y
)
e
i
y
+
i
sin
y
)
.
f
(
z
)
=
e
x
x
(
cos
y
+
i
sin
y
)
+
i
y
(
cos
y
+
i
sin
y
)
+
i
sin
y
=
e
x
(
x
+
i
y
)
e
i
y
+
i
sin
y
.
f(z)=e^(x)(x(cos y+i sin y)+iy(cos y+i sin y)+i sin y)=e^(x)((x+iy)e^(iy)+i sin y). f(z) = e^x \left( x (\cos y + i \sin y) + i y (\cos y + i \sin y) + i \sin y \right) = e^x \left( (x + i y) e^{i y} + i \sin y \right). f ( z ) = e x ( x ( cos y + i sin y ) + i y ( cos y + i sin y ) + i sin y ) = e x ( ( x + i y ) e i y + i sin y ) .
However, a simpler form can be obtained by noting that:
f
(
z
)
=
e
z
(
z
+
i
)
+
C
,
f
(
z
)
=
e
z
(
z
+
i
)
+
C
,
f(z)=e^(z)(z+i)+C, f(z) = e^z (z + i) + C, f ( z ) = e z ( z + i ) + C ,
where
C
C
C C C is a constant (here,
C
=
0
C
=
0
C=0 C = 0 C = 0 for the principal branch).
Verification:
Let
z
=
x
+
i
y
z
=
x
+
i
y
z=x+iy z = x + iy z = x + i y , then:
e
z
(
z
+
i
)
=
e
x
(
cos
y
+
i
sin
y
)
(
(
x
+
i
y
)
+
i
)
=
e
x
(
(
x
+
i
(
y
+
1
)
)
(
cos
y
+
i
sin
y
)
)
.
e
z
(
z
+
i
)
=
e
x
(
cos
y
+
i
sin
y
)
(
x
+
i
y
)
+
i
=
e
x
(
x
+
i
(
y
+
1
)
)
(
cos
y
+
i
sin
y
)
.
e^(z)(z+i)=e^(x)(cos y+i sin y)((x+iy)+i)=e^(x)((x+i(y+1))(cos y+i sin y)). e^z (z + i) = e^x (\cos y + i \sin y) \left( (x + iy) + i \right) = e^x \left( (x + i(y + 1)) (\cos y + i \sin y) \right). e z ( z + i ) = e x ( cos y + i sin y ) ( ( x + i y ) + i ) = e x ( ( x + i ( y + 1 ) ) ( cos y + i sin y ) ) .
Expanding:
=
e
x
(
x
cos
y
−
(
y
+
1
)
sin
y
+
i
(
x
sin
y
+
(
y
+
1
)
cos
y
)
)
.
=
e
x
x
cos
y
−
(
y
+
1
)
sin
y
+
i
x
sin
y
+
(
y
+
1
)
cos
y
.
=e^(x)(x cos y-(y+1)sin y+i(x sin y+(y+1)cos y)). = e^x \left( x \cos y – (y + 1) \sin y + i \left( x \sin y + (y + 1) \cos y \right) \right). = e x ( x cos y − ( y + 1 ) sin y + i ( x sin y + ( y + 1 ) cos y ) ) .
Comparing with
u
+
i
v
u
+
i
v
u+iv u + iv u + i v :
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
(
y
+
1
)
sin
y
+
sin
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
,
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
(
y
+
1
)
sin
y
+
sin
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
,
u(x,y)=e^(x)(x cos y-(y+1)sin y+sin y)=e^(x)(x cos y-y sin y), u(x, y) = e^x (x \cos y – (y + 1) \sin y + \sin y) = e^x (x \cos y – y \sin y), u ( x , y ) = e x ( x cos y − ( y + 1 ) sin y + sin y ) = e x ( x cos y − y sin y ) ,
v
(
x
,
y
)
=
e
x
(
x
sin
y
+
(
y
+
1
)
cos
y
−
cos
y
)
=
e
x
(
x
sin
y
+
y
cos
y
+
cos
y
−
cos
y
)
=
e
x
(
x
sin
y
+
y
cos
y
)
.
v
(
x
,
y
)
=
e
x
(
x
sin
y
+
(
y
+
1
)
cos
y
−
cos
y
)
=
e
x
(
x
sin
y
+
y
cos
y
+
cos
y
−
cos
y
)
=
e
x
(
x
sin
y
+
y
cos
y
)
.
v(x,y)=e^(x)(x sin y+(y+1)cos y-cos y)=e^(x)(x sin y+y cos y+cos y-cos y)=e^(x)(x sin y+y cos y). v(x, y) = e^x (x \sin y + (y + 1) \cos y – \cos y) = e^x (x \sin y + y \cos y + \cos y – \cos y) = e^x (x \sin y + y \cos y). v ( x , y ) = e x ( x sin y + ( y + 1 ) cos y − cos y ) = e x ( x sin y + y cos y + cos y − cos y ) = e x ( x sin y + y cos y ) .
Thus, the analytic function is:
f
(
z
)
=
e
z
(
z
+
i
)
.
f
(
z
)
=
e
z
(
z
+
i
)
.
f(z)=e^(z)(z+i). f(z) = e^z (z + i). f ( z ) = e z ( z + i ) .
Final Answer
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u
(
x
,
y
)
=
e
x
(
x
cos
y
−
y
sin
y
)
u(x,y)=e^(x)(x cos y-y sin y) u(x, y) = e^x (x \cos y – y \sin y) u ( x , y ) = e x ( x cos y − y sin y ) is harmonic.
The conjugate harmonic function is:
v
(
x
,
y
)
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
v
(
x
,
y
)
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
v(x,y)=e^(x)((x+1)sin y+y cos y). v(x, y) = e^x \left( (x + 1) \sin y + y \cos y \right). v ( x , y ) = e x ( ( x + 1 ) sin y + y cos y ) .
The corresponding analytic function is:
f
(
z
)
=
e
z
(
z
+
i
)
.
f
(
z
)
=
e
z
(
z
+
i
)
.
f(z)=e^(z)(z+i). f(z) = e^z (z + i). f ( z ) = e z ( z + i ) .
1.
u
(
x
,
y
)
is harmonic.
2. The conjugate harmonic function is
v
(
x
,
y
)
=
e
x
(
(
x
+
1
)
sin
y
+
y
cos
y
)
.
3. The analytic function is
f
(
z
)
=
e
z
(
z
+
i
)
.
1.
u
(
x
,
y
)
is harmonic.
2. The conjugate harmonic function is
v
(
x
,
y
)
=
e
x
(
x
+
1
)
sin
y
+
y
cos
y
.
3. The analytic function is
f
(
z
)
=
e
z
(
z
+
i
)
.
[“1. “u(x”,”y)” is harmonic.”],[“2. The conjugate harmonic function is “v(x”,”y)=e^(x)((x+1)sin y+y cos y).],[“3. The analytic function is “f(z)=e^(z)(z+i).] \boxed{
\begin{aligned}
&\text{1. } u(x, y) \text{ is harmonic.} \\
&\text{2. The conjugate harmonic function is } v(x, y) = e^x \left( (x + 1) \sin y + y \cos y \right). \\
&\text{3. The analytic function is } f(z) = e^z (z + i).
\end{aligned}
} 1. u ( x , y ) is harmonic. 2. The conjugate harmonic function is v ( x , y ) = e x ( ( x + 1 ) sin y + y cos y ) . 3. The analytic function is f ( z ) = e z ( z + i ) .
Question:-03 (c)
Solve the following linear programming problem by the Big M method:
Minimize
Z
=
2
x
1
+
3
x
2
Z
=
2
x
1
+
3
x
2
Z=2x_(1)+3x_(2) Z = 2x_1 + 3x_2 Z = 2 x 1 + 3 x 2
subject to
x
1
+
x
2
≥
9
x
1
+
2
x
2
≥
15
2
x
1
−
3
x
2
≤
9
x
1
,
x
2
≥
0
x
1
+
x
2
≥
9
x
1
+
2
x
2
≥
15
2
x
1
−
3
x
2
≤
9
x
1
,
x
2
≥
0
{:[x_(1)+x_(2) >= 9],[x_(1)+2x_(2) >= 15],[2x_(1)-3x_(2) <= 9],[x_(1)”,”x_(2) >= 0]:} \begin{aligned}
x_1 + x_2 &\geq 9 \\
x_1 + 2x_2 &\geq 15 \\
2x_1 – 3x_2 &\leq 9 \\
x_1, x_2 &\geq 0
\end{aligned} x 1 + x 2 ≥ 9 x 1 + 2 x 2 ≥ 15 2 x 1 − 3 x 2 ≤ 9 x 1 , x 2 ≥ 0
Is the optimal solution unique? Justify your answer.
Answer:
The given problem is:
Minimize
Z
=
2
x
1
+
3
x
2
Z
=
2
x
1
+
3
x
2
Z=2x_(1)+3x_(2) Z = 2x_1 + 3x_2 Z = 2 x 1 + 3 x 2
Subject to:
x
1
+
x
2
≥
9
,
x
1
+
2
x
2
≥
15
,
2
x
1
−
3
x
2
≤
9
,
x
1
,
x
2
≥
0.
x
1
+
x
2
≥
9
,
x
1
+
2
x
2
≥
15
,
2
x
1
−
3
x
2
≤
9
,
x
1
,
x
2
≥
0.
{:[x_(1)+x_(2) >= 9″,”],[x_(1)+2x_(2) >= 15″,”],[2x_(1)-3x_(2) <= 9″,”],[x_(1)”,”x_(2) >= 0.]:} \begin{aligned}
x_1 + x_2 &\geq 9, \\
x_1 + 2x_2 &\geq 15, \\
2x_1 – 3x_2 &\leq 9, \\
x_1, x_2 &\geq 0.
\end{aligned} x 1 + x 2 ≥ 9 , x 1 + 2 x 2 ≥ 15 , 2 x 1 − 3 x 2 ≤ 9 , x 1 , x 2 ≥ 0.
Convert to standard form (equality constraints):
For
x
1
+
x
2
≥
9
x
1
+
x
2
≥
9
x_(1)+x_(2) >= 9 x_1 + x_2 \geq 9 x 1 + x 2 ≥ 9 :
Subtract surplus variable
s
1
s
1
s_(1) s_1 s 1 and add artificial variable
A
1
A
1
A_(1) A_1 A 1 :
x
1
+
x
2
−
s
1
+
A
1
=
9.
x
1
+
x
2
−
s
1
+
A
1
=
9.
x_(1)+x_(2)-s_(1)+A_(1)=9. x_1 + x_2 – s_1 + A_1 = 9. x 1 + x 2 − s 1 + A 1 = 9.
For
x
1
+
2
x
2
≥
15
x
1
+
2
x
2
≥
15
x_(1)+2x_(2) >= 15 x_1 + 2x_2 \geq 15 x 1 + 2 x 2 ≥ 15 :
Subtract surplus variable
s
2
s
2
s_(2) s_2 s 2 and add artificial variable
A
2
A
2
A_(2) A_2 A 2 :
x
1
+
2
x
2
−
s
2
+
A
2
=
15.
x
1
+
2
x
2
−
s
2
+
A
2
=
15.
x_(1)+2x_(2)-s_(2)+A_(2)=15. x_1 + 2x_2 – s_2 + A_2 = 15. x 1 + 2 x 2 − s 2 + A 2 = 15.
For
2
x
1
−
3
x
2
≤
9
2
x
1
−
3
x
2
≤
9
2x_(1)-3x_(2) <= 9 2x_1 – 3x_2 \leq 9 2 x 1 − 3 x 2 ≤ 9 :
Add slack variable
s
3
s
3
s_(3) s_3 s 3 :
2
x
1
−
3
x
2
+
s
3
=
9.
2
x
1
−
3
x
2
+
s
3
=
9.
2x_(1)-3x_(2)+s_(3)=9. 2x_1 – 3x_2 + s_3 = 9. 2 x 1 − 3 x 2 + s 3 = 9.
Since we are minimizing
Z
=
2
x
1
+
3
x
2
Z
=
2
x
1
+
3
x
2
Z=2x_(1)+3x_(2) Z = 2x_1 + 3x_2 Z = 2 x 1 + 3 x 2 , we penalize the artificial variables in the objective function with a large positive coefficient
M
M
M M M :
Z
′
=
2
x
1
+
3
x
2
+
M
A
1
+
M
A
2
.
Z
′
=
2
x
1
+
3
x
2
+
M
A
1
+
M
A
2
.
Z^(‘)=2x_(1)+3x_(2)+MA_(1)+MA_(2). Z’ = 2x_1 + 3x_2 + M A_1 + M A_2. Z ′ = 2 x 1 + 3 x 2 + M A 1 + M A 2 .
Step 3: Construct the Initial Simplex Tableau
The initial tableau is:
Basis
x
1
x
1
x_(1) x_1 x 1
x
2
x
2
x_(2) x_2 x 2
s
1
s
1
s_(1) s_1 s 1
s
2
s
2
s_(2) s_2 s 2
s
3
s
3
s_(3) s_3 s 3
A
1
A
1
A_(1) A_1 A 1
A
2
A
2
A_(2) A_2 A 2
RHS
A
1
A
1
A_(1) A_1 A 1
1
1
-1
0
0
1
0
9
A
2
A
2
A_(2) A_2 A 2
1
2
0
-1
0
0
1
15
s
3
s
3
s_(3) s_3 s 3
2
-3
0
0
1
0
0
9
Z’
2
+
2
M
2
+
2
M
2+2M 2 + 2M 2 + 2 M
3
+
3
M
3
+
3
M
3+3M 3 + 3M 3 + 3 M
−
M
−
M
-M -M − M
−
M
−
M
-M -M − M
0
0
0
24
M
24
M
24 M 24M 24 M
Iteration 1:
Entering Variable:
x
2
x
2
x_(2) x_2 x 2 (most positive coefficient in
Z
′
Z
′
Z^(‘) Z’ Z ′ ).
Leaving Variable:
A
2
A
2
A_(2) A_2 A 2 (min ratio test:
min
(
9
/
1
,
15
/
2
,
ignore
s
3
)
=
7.5
min
(
9
/
1
,
15
/
2
,
ignore
s
3
)
=
7.5
min(9//1,15//2,”ignore “s_(3))=7.5 \min(9/1, 15/2, \text{ignore } s_3) = 7.5 min ( 9 / 1 , 15 / 2 , ignore s 3 ) = 7.5 ).
Pivot on
x
2
x
2
x_(2) x_2 x 2 in the
A
2
A
2
A_(2) A_2 A 2 row:
New
A
2
row
=
Old
A
2
row
2
.
New
A
2
row
=
Old
A
2
row
2
.
“New “A_(2)” row”=(“Old “A_(2)” row”)/(2). \text{New } A_2 \text{ row} = \frac{\text{Old } A_2 \text{ row}}{2}. New A 2 row = Old A 2 row 2 .
New
A
1
row
=
Old
A
1
row
−
New
A
2
row
.
New
A
1
row
=
Old
A
1
row
−
New
A
2
row
.
“New “A_(1)” row”=”Old “A_(1)” row”-“New “A_(2)” row”. \text{New } A_1 \text{ row} = \text{Old } A_1 \text{ row} – \text{New } A_2 \text{ row}. New A 1 row = Old A 1 row − New A 2 row .
New
s
3
row
=
Old
s
3
row
+
3
×
New
A
2
row
.
New
s
3
row
=
Old
s
3
row
+
3
×
New
A
2
row
.
“New “s_(3)” row”=”Old “s_(3)” row”+3xx”New “A_(2)” row”. \text{New } s_3 \text{ row} = \text{Old } s_3 \text{ row} + 3 \times \text{New } A_2 \text{ row}. New s 3 row = Old s 3 row + 3 × New A 2 row .
Updated Tableau:
Basis
x
1
x
1
x_(1) x_1 x 1
x
2
x
2
x_(2) x_2 x 2
s
1
s
1
s_(1) s_1 s 1
s
2
s
2
s_(2) s_2 s 2
s
3
s
3
s_(3) s_3 s 3
A
1
A
1
A_(1) A_1 A 1
A
2
A
2
A_(2) A_2 A 2
RHS
A
1
A
1
A_(1) A_1 A 1
0.5
0
-1
0.5
0
1
-0.5
1.5
x
2
x
2
x_(2) x_2 x 2
0.5
1
0
-0.5
0
0
0.5
7.5
s
3
s
3
s_(3) s_3 s 3
3.5
0
0
-1.5
1
0
1.5
31.5
Z’
0.5
+
0.5
M
0.5
+
0.5
M
0.5+0.5 M 0.5 + 0.5M 0.5 + 0.5 M
0
−
M
−
M
-M -M − M
1.5
+
1.5
M
1.5
+
1.5
M
1.5+1.5 M 1.5 + 1.5M 1.5 + 1.5 M
0
0
−
1.5
−
1.5
M
−
1.5
−
1.5
M
-1.5-1.5 M -1.5 – 1.5M − 1.5 − 1.5 M
22.5
−
1.5
M
22.5
−
1.5
M
22.5-1.5 M 22.5 – 1.5M 22.5 − 1.5 M
Iteration 2:
Entering Variable:
x
1
x
1
x_(1) x_1 x 1 .
Leaving Variable:
A
1
A
1
A_(1) A_1 A 1 (min ratio test:
min
(
1.5
/
0.5
,
7.5
/
0.5
,
31.5
/
3.5
)
=
3
min
(
1.5
/
0.5
,
7.5
/
0.5
,
31.5
/
3.5
)
=
3
min(1.5//0.5,7.5//0.5,31.5//3.5)=3 \min(1.5/0.5, 7.5/0.5, 31.5/3.5) = 3 min ( 1.5 / 0.5 , 7.5 / 0.5 , 31.5 / 3.5 ) = 3 ).
Pivot on
x
1
x
1
x_(1) x_1 x 1 in the
A
1
A
1
A_(1) A_1 A 1 row:
New
A
1
row
=
Old
A
1
row
0.5
.
New
A
1
row
=
Old
A
1
row
0.5
.
“New “A_(1)” row”=(“Old “A_(1)” row”)/(0.5). \text{New } A_1 \text{ row} = \frac{\text{Old } A_1 \text{ row}}{0.5}. New A 1 row = Old A 1 row 0.5 .
New
x
2
row
=
Old
x
2
row
−
0.5
×
New
A
1
row
.
New
x
2
row
=
Old
x
2
row
−
0.5
×
New
A
1
row
.
“New “x_(2)” row”=”Old “x_(2)” row”-0.5 xx”New “A_(1)” row”. \text{New } x_2 \text{ row} = \text{Old } x_2 \text{ row} – 0.5 \times \text{New } A_1 \text{ row}. New x 2 row = Old x 2 row − 0.5 × New A 1 row .
New
s
3
row
=
Old
s
3
row
−
3.5
×
New
A
1
row
.
New
s
3
row
=
Old
s
3
row
−
3.5
×
New
A
1
row
.
“New “s_(3)” row”=”Old “s_(3)” row”-3.5 xx”New “A_(1)” row”. \text{New } s_3 \text{ row} = \text{Old } s_3 \text{ row} – 3.5 \times \text{New } A_1 \text{ row}. New s 3 row = Old s 3 row − 3.5 × New A 1 row .
Updated Tableau:
Basis
x
1
x
1
x_(1) x_1 x 1
x
2
x
2
x_(2) x_2 x 2
s
1
s
1
s_(1) s_1 s 1
s
2
s
2
s_(2) s_2 s 2
s
3
s
3
s_(3) s_3 s 3
A
1
A
1
A_(1) A_1 A 1
A
2
A
2
A_(2) A_2 A 2
RHS
x
1
x
1
x_(1) x_1 x 1
1
0
-2
1
0
2
-1
3
x
2
x
2
x_(2) x_2 x 2
0
1
1
-1
0
-1
1
6
s
3
s
3
s_(3) s_3 s 3
0
0
7
-5
1
-7
5
21
Z’
0
0
1
−
2
M
1
−
2
M
1-2M 1 – 2M 1 − 2 M
1
+
M
1
+
M
1+M 1 + M 1 + M
0
−
1
+
2
M
−
1
+
2
M
-1+2M -1 + 2M − 1 + 2 M
−
1
−
M
−
1
−
M
-1-M -1 – M − 1 − M
21
Iteration 3:
Optimality Check: All coefficients in
Z
′
Z
′
Z^(‘) Z’ Z ′ are non-positive (since
M
M
M M M is large and positive).
Artificial Variables:
A
1
A
1
A_(1) A_1 A 1 and
A
2
A
2
A_(2) A_2 A 2 are non-basic (coefficients are zero in
Z
′
Z
′
Z^(‘) Z’ Z ′ ), so they can be removed.
From the final tableau:
x
1
=
3
,
x
2
=
6
,
s
3
=
21.
x
1
=
3
,
x
2
=
6
,
s
3
=
21.
x_(1)=3,quadx_(2)=6,quads_(3)=21. x_1 = 3, \quad x_2 = 6, \quad s_3 = 21. x 1 = 3 , x 2 = 6 , s 3 = 21.
The minimum value of
Z
Z
Z Z Z is:
Z
=
2
(
3
)
+
3
(
6
)
=
24.
Z
=
2
(
3
)
+
3
(
6
)
=
24.
Z=2(3)+3(6)=24. Z = 2(3) + 3(6) = 24. Z = 2 ( 3 ) + 3 ( 6 ) = 24.
Step 6: Check Uniqueness of the Optimal Solution
Uniqueness Condition: If all non-basic variables in the final tableau have strictly negative coefficients in the
Z
Z
Z Z Z -row, the solution is unique.
Final
Z
Z
Z Z Z -row Coefficients:
For
s
1
:
1
−
2
M
(
Negative for large
M
)
,
For
s
2
:
1
+
M
(
Positive
)
,
For
A
1
:
−
1
+
2
M
(
Positive for large
M
)
,
For
A
2
:
−
1
−
M
(
Negative
)
.
For
s
1
:
1
−
2
M
(
Negative for large
M
)
,
For
s
2
:
1
+
M
(
Positive
)
,
For
A
1
:
−
1
+
2
M
(
Positive for large
M
)
,
For
A
2
:
−
1
−
M
(
Negative
)
.
“For “s_(1):1-2M quad(“Negative for large “M),”For “s_(2):1+M quad(“Positive”),”For “A_(1):-1+2M quad(“Positive for large “M),”For “A_(2):-1-M quad(“Negative”). \text{For } s_1: 1 – 2M \quad (\text{Negative for large } M), \\
\text{For } s_2: 1 + M \quad (\text{Positive}), \\
\text{For } A_1: -1 + 2M \quad (\text{Positive for large } M), \\
\text{For } A_2: -1 – M \quad (\text{Negative}). For s 1 : 1 − 2 M ( Negative for large M ) , For s 2 : 1 + M ( Positive ) , For A 1 : − 1 + 2 M ( Positive for large M ) , For A 2 : − 1 − M ( Negative ) .
Conclusion: Since the coefficient for
s
2
s
2
s_(2) s_2 s 2 is positive , there exists an alternative optimal solution . Thus, the optimal solution is not unique .
Final Answer
Optimal Solution:
x
1
=
3
x
1
=
3
x_(1)=3 x_1 = 3 x 1 = 3 ,
x
2
=
6
x
2
=
6
x_(2)=6 x_2 = 6 x 2 = 6 , with
Z
=
24
Z
=
24
Z=24 Z = 24 Z = 24 .
Uniqueness: The optimal solution is not unique because the coefficient of
s
2
s
2
s_(2) s_2 s 2 in the final
Z
Z
Z Z Z -row is positive.
Optimal Solution:
x
1
=
3
,
x
2
=
6
,
with
Z
=
24.
The optimal solution is not unique.
Optimal Solution:
x
1
=
3
,
x
2
=
6
,
with
Z
=
24.
The optimal solution is not unique.
[“Optimal Solution: “x_(1)=3″,”x_(2)=6″,”” with “Z=24.],[“The optimal solution is not unique.”] \boxed{
\begin{aligned}
&\text{Optimal Solution: } x_1 = 3, x_2 = 6, \text{ with } Z = 24. \\
&\text{The optimal solution is not unique.}
\end{aligned}
} Optimal Solution: x 1 = 3 , x 2 = 6 , with Z = 24. The optimal solution is not unique.
Question:-04
(a) Prove that the oscillation of a real-valued bounded function
f
f
f f f defined on
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ] is the supremum of the set
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
{|f(x_(1))-f(x_(2))|:x_(1),x_(2)in[a,b]} \{ |f(x_1) – f(x_2)| : x_1, x_2 \in [a, b] \} { | f ( x 1 ) − f ( x 2 ) | : x 1 , x 2 ∈ [ a , b ] } .
Answer:
Proof: Oscillation of a Bounded Function on
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ]
We aim to prove that the
oscillation of a bounded real-valued function
f
f
f f f on
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ] is equal to the
supremum of the set of absolute differences of
f
f
f f f over
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ] .
Definitions:
Oscillation of
f
f
f f f on
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ] :
osc
(
f
,
[
a
,
b
]
)
=
sup
x
∈
[
a
,
b
]
f
(
x
)
−
inf
x
∈
[
a
,
b
]
f
(
x
)
.
osc
(
f
,
[
a
,
b
]
)
=
sup
x
∈
[
a
,
b
]
f
(
x
)
−
inf
x
∈
[
a
,
b
]
f
(
x
)
.
“osc”(f,[a,b])=s u p_(x in[a,b])f(x)-i n f_(x in[a,b])f(x). \text{osc}(f, [a, b]) = \sup_{x \in [a, b]} f(x) – \inf_{x \in [a, b]} f(x). osc ( f , [ a , b ] ) = sup x ∈ [ a , b ] f ( x ) − inf x ∈ [ a , b ] f ( x ) .
Set of Absolute Differences:
S
=
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
.
S
=
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
.
S={|f(x_(1))-f(x_(2))|:x_(1),x_(2)in[a,b]}. S = \{ |f(x_1) – f(x_2)| : x_1, x_2 \in [a, b] \}. S = { | f ( x 1 ) − f ( x 2 ) | : x 1 , x 2 ∈ [ a , b ] } .
Goal:
Prove that:
osc
(
f
,
[
a
,
b
]
)
=
sup
S
.
osc
(
f
,
[
a
,
b
]
)
=
sup
S
.
“osc”(f,[a,b])=s u p S. \text{osc}(f, [a, b]) = \sup S. osc ( f , [ a , b ] ) = sup S .
Step 1: Show
osc
(
f
,
[
a
,
b
]
)
≥
sup
S
osc
(
f
,
[
a
,
b
]
)
≥
sup
S
“osc”(f,[a,b]) >= s u p S \text{osc}(f, [a, b]) \geq \sup S osc ( f , [ a , b ] ) ≥ sup S
By definition of supremum and infimum, for any
x
1
,
x
2
∈
[
a
,
b
]
x
1
,
x
2
∈
[
a
,
b
]
x_(1),x_(2)in[a,b] x_1, x_2 \in [a, b] x 1 , x 2 ∈ [ a , b ] :
f
(
x
1
)
≤
sup
x
∈
[
a
,
b
]
f
(
x
)
,
f
(
x
2
)
≥
inf
x
∈
[
a
,
b
]
f
(
x
)
.
f
(
x
1
)
≤
sup
x
∈
[
a
,
b
]
f
(
x
)
,
f
(
x
2
)
≥
inf
x
∈
[
a
,
b
]
f
(
x
)
.
f(x_(1)) <= s u p_(x in[a,b])f(x),quad f(x_(2)) >= i n f_(x in[a,b])f(x). f(x_1) \leq \sup_{x \in [a, b]} f(x), \quad f(x_2) \geq \inf_{x \in [a, b]} f(x). f ( x 1 ) ≤ sup x ∈ [ a , b ] f ( x ) , f ( x 2 ) ≥ inf x ∈ [ a , b ] f ( x ) .
Therefore:
|
f
(
x
1
)
−
f
(
x
2
)
|
≤
sup
f
−
inf
f
=
osc
(
f
,
[
a
,
b
]
)
.
|
f
(
x
1
)
−
f
(
x
2
)
|
≤
sup
f
−
inf
f
=
osc
(
f
,
[
a
,
b
]
)
.
|f(x_(1))-f(x_(2))| <= s u p f-i n f f=”osc”(f,[a,b]). |f(x_1) – f(x_2)| \leq \sup f – \inf f = \text{osc}(f, [a, b]). | f ( x 1 ) − f ( x 2 ) | ≤ sup f − inf f = osc ( f , [ a , b ] ) .
Since this holds for all
x
1
,
x
2
x
1
,
x
2
x_(1),x_(2) x_1, x_2 x 1 , x 2 , it follows that:
sup
S
≤
osc
(
f
,
[
a
,
b
]
)
.
sup
S
≤
osc
(
f
,
[
a
,
b
]
)
.
s u p S <= “osc”(f,[a,b]). \sup S \leq \text{osc}(f, [a, b]). sup S ≤ osc ( f , [ a , b ] ) .
Step 2: Show
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
“osc”(f,[a,b]) <= s u p S \text{osc}(f, [a, b]) \leq \sup S osc ( f , [ a , b ] ) ≤ sup S
Let
sup
f
=
f
(
x
∗
)
sup
f
=
f
(
x
∗
)
s u p f=f(x^(**)) \sup f = f(x^*) sup f = f ( x ∗ ) and
inf
f
=
f
(
x
∗
)
inf
f
=
f
(
x
∗
)
i n f f=f(x_(**)) \inf f = f(x_*) inf f = f ( x ∗ ) for some
x
∗
,
x
∗
∈
[
a
,
b
]
x
∗
,
x
∗
∈
[
a
,
b
]
x^(**),x_(**)in[a,b] x^*, x_* \in [a, b] x ∗ , x ∗ ∈ [ a , b ] (since
f
f
f f f is bounded and
[
a
,
b
]
[
a
,
b
]
[a,b] [a, b] [ a , b ] is compact, the supremum and infimum are attained).
Then:
osc
(
f
,
[
a
,
b
]
)
=
f
(
x
∗
)
−
f
(
x
∗
)
=
|
f
(
x
∗
)
−
f
(
x
∗
)
|
∈
S
.
osc
(
f
,
[
a
,
b
]
)
=
f
(
x
∗
)
−
f
(
x
∗
)
=
|
f
(
x
∗
)
−
f
(
x
∗
)
|
∈
S
.
“osc”(f,[a,b])=f(x^(**))-f(x_(**))=|f(x^(**))-f(x_(**))|in S. \text{osc}(f, [a, b]) = f(x^*) – f(x_*) = |f(x^*) – f(x_*)| \in S. osc ( f , [ a , b ] ) = f ( x ∗ ) − f ( x ∗ ) = | f ( x ∗ ) − f ( x ∗ ) | ∈ S .
Since
sup
S
sup
S
s u p S \sup S sup S is the least upper bound of
S
S
S S S , and
osc
(
f
,
[
a
,
b
]
)
∈
S
osc
(
f
,
[
a
,
b
]
)
∈
S
“osc”(f,[a,b])in S \text{osc}(f, [a, b]) \in S osc ( f , [ a , b ] ) ∈ S , we have:
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
.
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
.
“osc”(f,[a,b]) <= s u p S. \text{osc}(f, [a, b]) \leq \sup S. osc ( f , [ a , b ] ) ≤ sup S .
Step 3: Conclusion
From Steps 1 and 2, we have:
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
≤
osc
(
f
,
[
a
,
b
]
)
.
osc
(
f
,
[
a
,
b
]
)
≤
sup
S
≤
osc
(
f
,
[
a
,
b
]
)
.
“osc”(f,[a,b]) <= s u p S <= “osc”(f,[a,b]). \text{osc}(f, [a, b]) \leq \sup S \leq \text{osc}(f, [a, b]). osc ( f , [ a , b ] ) ≤ sup S ≤ osc ( f , [ a , b ] ) .
Thus:
osc
(
f
,
[
a
,
b
]
)
=
sup
S
.
osc
(
f
,
[
a
,
b
]
)
=
sup
S
.
“osc”(f,[a,b])=s u p S. \text{osc}(f, [a, b]) = \sup S. osc ( f , [ a , b ] ) = sup S .
Final Answer
osc
(
f
,
[
a
,
b
]
)
=
sup
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
osc
(
f
,
[
a
,
b
]
)
=
sup
{
|
f
(
x
1
)
−
f
(
x
2
)
|
:
x
1
,
x
2
∈
[
a
,
b
]
}
“osc”(f,[a,b])=s u p{|f(x_(1))-f(x_(2))|:x_(1),x_(2)in[a,b]} \boxed{\text{osc}(f, [a, b]) = \sup \{ |f(x_1) – f(x_2)| : x_1, x_2 \in [a, b] \}} osc ( f , [ a , b ] ) = sup { | f ( x 1 ) − f ( x 2 ) | : x 1 , x 2 ∈ [ a , b ] }
Question:-04 (b)
Classify the singular point
z
=
0
z
=
0
z=0 z = 0 z = 0 of the function
f
(
z
)
=
e
z
z
−
sin
z
f
(
z
)
=
e
z
z
−
sin
z
f(z)=(e^(z))/(z-sin z) f(z) = \frac{e^z}{z – \sin z} f ( z ) = e z z − sin z and obtain the principal part of its Laurent series expansion.
Answer:
To classify the singular point
z
=
0
z
=
0
z=0 z = 0 z = 0 of the function
f
(
z
)
=
e
z
z
−
sin
z
f
(
z
)
=
e
z
z
−
sin
z
f(z)=(e^(z))/(z-sin z) f(z) = \frac{e^z}{z – \sin z} f ( z ) = e z z − sin z and find the principal part of its Laurent series expansion, we proceed with the following steps:
Step 1: Analyze the Denominator
z
−
sin
z
z
−
sin
z
z-sin z z – \sin z z − sin z Near
z
=
0
z
=
0
z=0 z = 0 z = 0
First, expand
sin
z
sin
z
sin z \sin z sin z in a Taylor series around
z
=
0
z
=
0
z=0 z = 0 z = 0 :
sin
z
=
z
−
z
3
6
+
z
5
120
−
⋯
sin
z
=
z
−
z
3
6
+
z
5
120
−
⋯
sin z=z-(z^(3))/(6)+(z^(5))/(120)-cdots \sin z = z – \frac{z^3}{6} + \frac{z^5}{120} – \cdots sin z = z − z 3 6 + z 5 120 − ⋯
Thus, the denominator becomes:
z
−
sin
z
=
z
3
6
−
z
5
120
+
⋯
=
z
3
6
(
1
−
z
2
20
+
⋯
)
.
z
−
sin
z
=
z
3
6
−
z
5
120
+
⋯
=
z
3
6
1
−
z
2
20
+
⋯
.
z-sin z=(z^(3))/(6)-(z^(5))/(120)+cdots=(z^(3))/(6)(1-(z^(2))/(20)+cdots). z – \sin z = \frac{z^3}{6} – \frac{z^5}{120} + \cdots = \frac{z^3}{6} \left(1 – \frac{z^2}{20} + \cdots \right). z − sin z = z 3 6 − z 5 120 + ⋯ = z 3 6 ( 1 − z 2 20 + ⋯ ) .
This shows that
z
−
sin
z
z
−
sin
z
z-sin z z – \sin z z − sin z has a
zero of order 3 at
z
=
0
z
=
0
z=0 z = 0 z = 0 .
Step 2: Analyze the Numerator
e
z
e
z
e^(z) e^z e z Near
z
=
0
z
=
0
z=0 z = 0 z = 0
The Taylor series for
e
z
e
z
e^(z) e^z e z around
z
=
0
z
=
0
z=0 z = 0 z = 0 is:
e
z
=
1
+
z
+
z
2
2
+
z
3
6
+
⋯
e
z
=
1
+
z
+
z
2
2
+
z
3
6
+
⋯
e^(z)=1+z+(z^(2))/(2)+(z^(3))/(6)+cdots e^z = 1 + z + \frac{z^2}{2} + \frac{z^3}{6} + \cdots e z = 1 + z + z 2 2 + z 3 6 + ⋯
The numerator
e
z
e
z
e^(z) e^z e z is
non-zero and analytic at
z
=
0
z
=
0
z=0 z = 0 z = 0 .
Step 3: Determine the Nature of the Singularity
The function
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) can be written as:
f
(
z
)
=
e
z
z
−
sin
z
=
1
+
z
+
z
2
2
+
z
3
6
+
⋯
z
3
6
(
1
−
z
2
20
+
⋯
)
.
f
(
z
)
=
e
z
z
−
sin
z
=
1
+
z
+
z
2
2
+
z
3
6
+
⋯
z
3
6
1
−
z
2
20
+
⋯
.
f(z)=(e^(z))/(z-sin z)=(1+z+(z^(2))/(2)+(z^(3))/(6)+cdots)/((z^(3))/(6)(1-(z^(2))/(20)+cdots)). f(z) = \frac{e^z}{z – \sin z} = \frac{1 + z + \frac{z^2}{2} + \frac{z^3}{6} + \cdots}{\frac{z^3}{6} \left(1 – \frac{z^2}{20} + \cdots \right)}. f ( z ) = e z z − sin z = 1 + z + z 2 2 + z 3 6 + ⋯ z 3 6 ( 1 − z 2 20 + ⋯ ) .
Since the denominator has a zero of order 3 and the numerator is non-zero,
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) has a
pole of order 3 at
z
=
0
z
=
0
z=0 z = 0 z = 0 .
Step 4: Find the Laurent Series Expansion Near
z
=
0
z
=
0
z=0 z = 0 z = 0
To find the principal part of the Laurent series, we perform long division or expand
e
z
z
−
sin
z
e
z
z
−
sin
z
(e^(z))/(z-sin z) \frac{e^z}{z – \sin z} e z z − sin z in powers of
z
z
z z z .
First, express
f
(
z
)
f
(
z
)
f(z) f(z) f ( z ) as:
f
(
z
)
=
6
e
z
z
3
(
1
−
z
2
20
+
⋯
)
.
f
(
z
)
=
6
e
z
z
3
1
−
z
2
20
+
⋯
.
f(z)=(6e^(z))/(z^(3)(1-(z^(2))/(20)+cdots)). f(z) = \frac{6 e^z}{z^3 \left(1 – \frac{z^2}{20} + \cdots \right)}. f ( z ) = 6 e z z 3 ( 1 − z 2 20 + ⋯ ) .
Using the geometric series expansion for the denominator:
1
1
−
z
2
20
+
⋯
=
1
+
z
2
20
+
⋯
,
1
1
−
z
2
20
+
⋯
=
1
+
z
2
20
+
⋯
,
(1)/(1-(z^(2))/(20)+cdots)=1+(z^(2))/(20)+cdots, \frac{1}{1 – \frac{z^2}{20} + \cdots} = 1 + \frac{z^2}{20} + \cdots, 1 1 − z 2 20 + ⋯ = 1 + z 2 20 + ⋯ ,
we get:
f
(
z
)
=
6
z
3
(
1
+
z
+
z
2
2
+
z
3
6
+
⋯
)
(
1
+
z
2
20
+
⋯
)
.
f
(
z
)
=
6
z
3
1
+
z
+
z
2
2
+
z
3
6
+
⋯
1
+
z
2
20
+
⋯
.
f(z)=(6)/(z^(3))(1+z+(z^(2))/(2)+(z^(3))/(6)+cdots)(1+(z^(2))/(20)+cdots). f(z) = \frac{6}{z^3} \left(1 + z + \frac{z^2}{2} + \frac{z^3}{6} + \cdots \right) \left(1 + \frac{z^2}{20} + \cdots \right). f ( z ) = 6 z 3 ( 1 + z + z 2 2 + z 3 6 + ⋯ ) ( 1 + z 2 20 + ⋯ ) .
Multiplying the series:
f
(
z
)
=
6
z
3
(
1
+
z
+
(
1
2
+
1
20
)
z
2
+
(
1
6
+
1
20
)
z
3
+
⋯
)
.
f
(
z
)
=
6
z
3
1
+
z
+
1
2
+
1
20
z
2
+
1
6
+
1
20
z
3
+
⋯
.
f(z)=(6)/(z^(3))(1+z+((1)/(2)+(1)/(20))z^(2)+((1)/(6)+(1)/(20))z^(3)+cdots). f(z) = \frac{6}{z^3} \left(1 + z + \left(\frac{1}{2} + \frac{1}{20}\right) z^2 + \left(\frac{1}{6} + \frac{1}{20}\right) z^3 + \cdots \right). f ( z ) = 6 z 3 ( 1 + z + ( 1 2 + 1 20 ) z 2 + ( 1 6 + 1 20 ) z 3 + ⋯ ) .
Simplifying:
f
(
z
)
=
6
z
3
+
6
z
2
+
21
5
z
+
23
10
+
⋯
.
f
(
z
)
=
6
z
3
+
6
z
2
+
21
5
z
+
23
10
+
⋯
.
f(z)=(6)/(z^(3))+(6)/(z^(2))+(21)/(5z)+(23)/(10)+cdots. f(z) = \frac{6}{z^3} + \frac{6}{z^2} + \frac{21}{5z} + \frac{23}{10} + \cdots. f ( z ) = 6 z 3 + 6 z 2 + 21 5 z + 23 10 + ⋯ .
Step 5: Identify the Principal Part
The principal part of the Laurent series consists of the terms with negative powers of
z
z
z z z :
Principal Part
=
6
z
3
+
6
z
2
+
21
5
z
.
Principal Part
=
6
z
3
+
6
z
2
+
21
5
z
.
“Principal Part”=(6)/(z^(3))+(6)/(z^(2))+(21)/(5z). \text{Principal Part} = \frac{6}{z^3} + \frac{6}{z^2} + \frac{21}{5z}. Principal Part = 6 z 3 + 6 z 2 + 21 5 z .
Final Answer
Classification:
z
=
0
z
=
0
z=0 z = 0 z = 0 is a pole of order 3 .
Principal Part of Laurent Series:
6
z
3
+
6
z
2
+
21
5
z
6
z
3
+
6
z
2
+
21
5
z
(6)/(z^(3))+(6)/(z^(2))+(21)/(5z) \boxed{ \frac{6}{z^3} + \frac{6}{z^2} + \frac{21}{5z} } 6 z 3 + 6 z 2 + 21 5 z
Question:-04 (c)
Jobs
A
B
C
D
E
I
4
9
4
12
4
II
15
11
20
5
8
III
17
7
15
12
18
IV
9
13
11
9
14
V
6
11
12
9
14
How should the jobs be assigned, one to each subordinate, so as to minimize the total time? Also, obtain the total minimum time to perform all the jobs if subordinate IV cannot be assigned job C.
Answer:
This is the original cost matrix:
4 9 4 12 4
15 11 20 5 8
17 7 15 12 18
6 13 11 9 14
Subtract row minima
We subtract the row minimum from each row:
0 5 0 8 0 (-4)
10 6 15 0 3 (-5)
10 0 8 5 11 (-7)
0 7 5 3 8 (-6)
Subtract column minima
Because each column contains a zero, subtracting column minima has no effect.
Cover all zeros with a minimum number of lines
There are 4 lines required to cover all zeros:
10 5 0 0 3 x
10 0 8 5 11 x
0 7 5 3 8 x
x 0 0 0 3 x
Create additional zeros
The number of lines is smaller than 5. The smallest uncovered number is 2. We subtract this number from all uncovered elements and add it to all elements that are covered twice:
2 5 0 10 0
10 4 13 0 1
12 0 8 7 11
0 2 0 0 3
0 3 4 3 6
Cover all zeros with a minimum number of lines
There are 5 lines required to cover all zeros:
2 5 0 10 0 x
12 0 8 0 1 x
0 0 0 7 11 x
0 2 0 0 3 x
x 3 4 3 6 x
The optimal assignment
Because there are 5 lines required, the zeros cover an optimal assignment:
2 5 0 10 0
12 0 8 0 1
0 0 0 7 11
0 2 0 0 3
This corresponds to the following 4 to 4 assignment in the original cost matrix:
4 9 4 12 4
15 11 20 5 8
17 7 15 12 18
6 13 11 9 14
The optimal value equals 33.
Question:-05 (c)
Evaluate, using binary arithmetic, the following numbers in their given system:
(i)
(
634.235
)
8
−
(
132.223
)
8
(
634.235
)
8
−
(
132.223
)
8
(634.235)_(8)-(132.223)_(8) (634.235)_8 – (132.223)_8 ( 634.235 ) 8 − ( 132.223 ) 8
(ii)
(
7
A
B
.432
)
16
−
(
5
C
A
.
D
61
)
16
(
7
A
B
.432
)
16
−
(
5
C
A
.
D
61
)
16
(7AB.432)_(16)-(5CA.D 61)_(16) (7AB.432)_{16} – (5CA.D61)_{16} ( 7 A B .432 ) 16 − ( 5 C A . D 61 ) 16
Answer:
Solution:
(i)
(
634.235
)
8
−
(
132.223
)
8
(
634.235
)
8
−
(
132.223
)
8
(634.235)_(8)-(132.223)_(8) (634.235)_8 – (132.223)_8 ( 634.235 ) 8 − ( 132.223 ) 8 )
Step 1: Convert both octal numbers to binary.
(
634.235
)
8
(
634.235
)
8
(634.235)_(8) (634.235)_8 ( 634.235 ) 8 to binary:
6
→
110
,
3
→
011
,
4
→
100
,
.
2
→
010
,
3
→
011
,
5
→
101
6
→
110
,
3
→
011
,
4
→
100
,
.
2
→
010
,
3
→
011
,
5
→
101
6rarr110,quad3rarr011,quad4rarr100,quad.quad2rarr010,quad3rarr011,quad5rarr101 6 \rightarrow 110, \quad 3 \rightarrow 011, \quad 4 \rightarrow 100, \quad . \quad 2 \rightarrow 010, \quad 3 \rightarrow 011, \quad 5 \rightarrow 101 6 → 110 , 3 → 011 , 4 → 100 , . 2 → 010 , 3 → 011 , 5 → 101
(
634.235
)
8
=
(
110
011
100.010
011
101
)
2
(
634.235
)
8
=
(
110
011
100.010
011
101
)
2
(634.235)_(8)=(110011100.010011101)_(2) (634.235)_8 = (110\,011\,100.010\,011\,101)_2 ( 634.235 ) 8 = ( 110 011 100.010 011 101 ) 2
(
132.223
)
8
(
132.223
)
8
(132.223)_(8) (132.223)_8 ( 132.223 ) 8 to binary:
1
→
001
,
3
→
011
,
2
→
010
,
.
2
→
010
,
2
→
010
,
3
→
011
1
→
001
,
3
→
011
,
2
→
010
,
.
2
→
010
,
2
→
010
,
3
→
011
1rarr001,quad3rarr011,quad2rarr010,quad.quad2rarr010,quad2rarr010,quad3rarr011 1 \rightarrow 001, \quad 3 \rightarrow 011, \quad 2 \rightarrow 010, \quad . \quad 2 \rightarrow 010, \quad 2 \rightarrow 010, \quad 3 \rightarrow 011 1 → 001 , 3 → 011 , 2 → 010 , . 2 → 010 , 2 → 010 , 3 → 011
(
132.223
)
8
=
(
001
011
010.010
010
011
)
2
(
132.223
)
8
=
(
001
011
010.010
010
011
)
2
(132.223)_(8)=(001011010.010010011)_(2) (132.223)_8 = (001\,011\,010.010\,010\,011)_2 ( 132.223 ) 8 = ( 001 011 010.010 010 011 ) 2
Step 2: Perform binary subtraction.
−
110
011
100.010
011
101
−
001
011
010.010
010
011
−
110
011
100.010
011
101
−
001
011
010.010
010
011
-110011100.010011101-001011010.010010011 \begin{array}{r}
\phantom{-}110\,011\,100.010\,011\,101 \\
-\;001\,011\,010.010\,010\,011 \\
\hline
\end{array} − 110 011 100.010 011 101 − 001 011 010.010 010 011
Subtraction process (using two’s complement for negative results):
110
011
100.010
011
101
−
001
011
010.010
010
011
=
101
000
010.000
001
010
110
011
100.010
011
101
−
001
011
010.010
010
011
=
101
000
010.000
001
010
110011100.010011101-001011010.010010011=101000010.000001010 110\,011\,100.010\,011\,101 – 001\,011\,010.010\,010\,011 = 101\,000\,010.000\,001\,010 110 011 100.010 011 101 − 001 011 010.010 010 011 = 101 000 010.000 001 010
Step 3: Convert the result back to octal.
101
000
010.000
001
010
→
5
0
2.0
1
2
101
000
010.000
001
010
→
5
0
2.0
1
2
101000010.000001010 rarr502.012 101\,000\,010.000\,001\,010 \rightarrow 5\,0\,2.0\,1\,2 101 000 010.000 001 010 → 5 0 2.0 1 2
(
502.012
)
8
(
502.012
)
8
(502.012)_(8) (502.012)_8 ( 502.012 ) 8
Final Answer:
(
502.012
)
8
(
502.012
)
8
(502.012)_(8) \boxed{(502.012)_8} ( 502.012 ) 8
(ii)
(
7
A
B
.432
)
16
−
(
5
C
A
.
D
61
)
16
(
7
A
B
.432
)
16
−
(
5
C
A
.
D
61
)
16
(7AB.432)_(16)-(5CA.D 61)_(16) (7AB.432)_{16} – (5CA.D61)_{16} ( 7 A B .432 ) 16 − ( 5 C A . D 61 ) 16 )
Step 1: Convert both hexadecimal numbers to binary.
(
7
A
B
.432
)
16
(
7
A
B
.432
)
16
(7AB.432)_(16) (7AB.432)_{16} ( 7 A B .432 ) 16 to binary:
7
→
0111
,
A
→
1010
,
B
→
1011
,
.
4
→
0100
,
3
→
0011
,
2
→
0010
7
→
0111
,
A
→
1010
,
B
→
1011
,
.
4
→
0100
,
3
→
0011
,
2
→
0010
7rarr0111,quad A rarr1010,quad B rarr1011,quad.quad4rarr0100,quad3rarr0011,quad2rarr0010 7 \rightarrow 0111, \quad A \rightarrow 1010, \quad B \rightarrow 1011, \quad . \quad 4 \rightarrow 0100, \quad 3 \rightarrow 0011, \quad 2 \rightarrow 0010 7 → 0111 , A → 1010 , B → 1011 , . 4 → 0100 , 3 → 0011 , 2 → 0010
(
7
A
B
.432
)
16
=
(
0111
1010
1011.0100
0011
0010
)
2
(
7
A
B
.432
)
16
=
(
0111
1010
1011.0100
0011
0010
)
2
(7AB.432)_(16)=(011110101011.010000110010)_(2) (7AB.432)_{16} = (0111\,1010\,1011.0100\,0011\,0010)_2 ( 7 A B .432 ) 16 = ( 0111 1010 1011.0100 0011 0010 ) 2
(
5
C
A
.
D
61
)
16
(
5
C
A
.
D
61
)
16
(5CA.D 61)_(16) (5CA.D61)_{16} ( 5 C A . D 61 ) 16 to binary:
5
→
0101
,
C
→
1100
,
A
→
1010
,
.
D
→
1101
,
6
→
0110
,
1
→
0001
5
→
0101
,
C
→
1100
,
A
→
1010
,
.
D
→
1101
,
6
→
0110
,
1
→
0001
5rarr0101,quad C rarr1100,quad A rarr1010,quad.quad D rarr1101,quad6rarr0110,quad1rarr0001 5 \rightarrow 0101, \quad C \rightarrow 1100, \quad A \rightarrow 1010, \quad . \quad D \rightarrow 1101, \quad 6 \rightarrow 0110, \quad 1 \rightarrow 0001 5 → 0101 , C → 1100 , A → 1010 , . D → 1101 , 6 → 0110 , 1 → 0001
(
5
C
A
.
D
61
)
16
=
(
0101
1100
1010.1101
0110
0001
)
2
(
5
C
A
.
D
61
)
16
=
(
0101
1100
1010.1101
0110
0001
)
2
(5CA.D 61)_(16)=(010111001010.110101100001)_(2) (5CA.D61)_{16} = (0101\,1100\,1010.1101\,0110\,0001)_2 ( 5 C A . D 61 ) 16 = ( 0101 1100 1010.1101 0110 0001 ) 2
Step 2: Perform binary subtraction.
−
0111
1010
1011.0100
0011
0010
−
0101
1100
1010.1101
0110
0001
−
0111
1010
1011.0100
0011
0010
−
0101
1100
1010.1101
0110
0001
-011110101011.010000110010-010111001010.110101100001 \begin{array}{r}
\phantom{-}0111\,1010\,1011.0100\,0011\,0010 \\
-\;0101\,1100\,1010.1101\,0110\,0001 \\
\hline
\end{array} − 0111 1010 1011.0100 0011 0010 − 0101 1100 1010.1101 0110 0001
Subtraction process (using two’s complement for negative results):
0111
1010
1011.0100
0011
0010
−
0101
1100
1010.1101
0110
0001
=
0001
1101
1100.0110
1101
0001
0111
1010
1011.0100
0011
0010
−
0101
1100
1010.1101
0110
0001
=
0001
1101
1100.0110
1101
0001
011110101011.010000110010-010111001010.110101100001=000111011100.011011010001 0111\,1010\,1011.0100\,0011\,0010 – 0101\,1100\,1010.1101\,0110\,0001 = 0001\,1101\,1100.0110\,1101\,0001 0111 1010 1011.0100 0011 0010 − 0101 1100 1010.1101 0110 0001 = 0001 1101 1100.0110 1101 0001
Step 3: Convert the result back to hexadecimal.
0001
1101
1100.0110
1101
0001
→
1
D
C
.6
D
1
0001
1101
1100.0110
1101
0001
→
1
D
C
.6
D
1
000111011100.011011010001 rarr1DC.6D1 0001\,1101\,1100.0110\,1101\,0001 \rightarrow 1\,D\,C.6\,D\,1 0001 1101 1100.0110 1101 0001 → 1 D C .6 D 1
(
1
D
C
.6
D
1
)
16
(
1
D
C
.6
D
1
)
16
(1DC.6 D1)_(16) (1DC.6D1)_{16} ( 1 D C .6 D 1 ) 16
Final Answer:
(
1
D
C
.6
D
1
)
16
(
1
D
C
.6
D
1
)
16
(1DC.6 D1)_(16) \boxed{(1DC.6D1)_{16}} ( 1 D C .6 D 1 ) 16
Question:-05 (d)
A planet of mass
m
m
m m m is revolving around the sun of mass
M
M
M M M . The kinetic energy
T
T
T T T and the potential energy
V
V
V V V of the planet are given by
T
=
1
2
m
(
r
˙
2
+
r
2
θ
˙
2
)
T
=
1
2
m
(
r
˙
2
+
r
2
θ
˙
2
)
T=(1)/(2)m(r^(˙)^(2)+r^(2)theta^(˙)^(2)) T = \frac{1}{2} m (\dot{r}^2 + r^2 \dot{\theta}^2) T = 1 2 m ( r ˙ 2 + r 2 θ ˙ 2 ) and
V
=
G
M
m
(
1
2
a
−
1
r
)
V
=
G
M
m
1
2
a
−
1
r
V=GMm((1)/(2a)-(1)/(r)) V = G M m \left( \frac{1}{2a} – \frac{1}{r} \right) V = G M m ( 1 2 a − 1 r ) , where
(
r
,
θ
)
(
r
,
θ
)
(r,theta) (r, \theta) ( r , θ ) are the polar coordinates of the planet at time
t
t
t t t ,
G
G
G G G is the gravitational constant, and
2
a
2
a
2a 2a 2 a is the major axis of the ellipse (the path of the planet). Find the Hamiltonian and the Hamilton equations of the planet’s motion.
Answer:
To find the Hamiltonian and the Hamilton equations for the planet’s motion, we follow these steps:
1. Lagrangian of the System
The Lagrangian
L
L
L L L is given by:
L
=
T
−
V
L
=
T
−
V
L=T-V L = T – V L = T − V
where:
Kinetic Energy (T):
T
=
1
2
m
(
r
˙
2
+
r
2
θ
˙
2
)
T
=
1
2
m
r
˙
2
+
r
2
θ
˙
2
T=(1)/(2)m(r^(˙)^(2)+r^(2)theta^(˙)^(2)) T = \frac{1}{2} m \left( \dot{r}^2 + r^2 \dot{\theta}^2 \right) T = 1 2 m ( r ˙ 2 + r 2 θ ˙ 2 )
Potential Energy (V):
V
=
G
M
m
(
1
2
a
−
1
r
)
V
=
G
M
m
1
2
a
−
1
r
V=GMm((1)/(2a)-(1)/(r)) V = G M m \left( \frac{1}{2a} – \frac{1}{r} \right) V = G M m ( 1 2 a − 1 r )
Thus:
L
=
1
2
m
(
r
˙
2
+
r
2
θ
˙
2
)
−
G
M
m
(
1
2
a
−
1
r
)
L
=
1
2
m
r
˙
2
+
r
2
θ
˙
2
−
G
M
m
1
2
a
−
1
r
L=(1)/(2)m(r^(˙)^(2)+r^(2)theta^(˙)^(2))-GMm((1)/(2a)-(1)/(r)) L = \frac{1}{2} m \left( \dot{r}^2 + r^2 \dot{\theta}^2 \right) – G M m \left( \frac{1}{2a} – \frac{1}{r} \right) L = 1 2 m ( r ˙ 2 + r 2 θ ˙ 2 ) − G M m ( 1 2 a − 1 r )
2. Generalized Momenta
The
generalized momenta
p
r
p
r
p_(r) p_r p r and
p
θ
p
θ
p_( theta) p_\theta p θ are obtained from:
p
r
=
∂
L
∂
r
˙
=
m
r
˙
p
r
=
∂
L
∂
r
˙
=
m
r
˙
p_(r)=(del L)/(del(r^(˙)))=mr^(˙) p_r = \frac{\partial L}{\partial \dot{r}} = m \dot{r} p r = ∂ L ∂ r ˙ = m r ˙
p
θ
=
∂
L
∂
θ
˙
=
m
r
2
θ
˙
p
θ
=
∂
L
∂
θ
˙
=
m
r
2
θ
˙
p_( theta)=(del L)/(del(theta^(˙)))=mr^(2)theta^(˙) p_\theta = \frac{\partial L}{\partial \dot{\theta}} = m r^2 \dot{\theta} p θ = ∂ L ∂ θ ˙ = m r 2 θ ˙
3. Hamiltonian
The Hamiltonian
H
H
H H H is defined as:
H
=
∑
i
p
i
q
˙
i
−
L
H
=
∑
i
p
i
q
˙
i
−
L
H=sum _(i)p_(i)q^(˙)_(i)-L H = \sum_i p_i \dot{q}_i – L H = ∑ i p i q ˙ i − L
Substituting the momenta and Lagrangian:
H
=
p
r
r
˙
+
p
θ
θ
˙
−
L
H
=
p
r
r
˙
+
p
θ
θ
˙
−
L
H=p_(r)r^(˙)+p_( theta)theta^(˙)-L H = p_r \dot{r} + p_\theta \dot{\theta} – L H = p r r ˙ + p θ θ ˙ − L
Express
r
˙
r
˙
r^(˙) \dot{r} r ˙ and
θ
˙
θ
˙
theta^(˙) \dot{\theta} θ ˙ in terms of
p
r
p
r
p_(r) p_r p r and
p
θ
p
θ
p_( theta) p_\theta p θ :
r
˙
=
p
r
m
,
θ
˙
=
p
θ
m
r
2
r
˙
=
p
r
m
,
θ
˙
=
p
θ
m
r
2
r^(˙)=(p_(r))/(m),quadtheta^(˙)=(p_( theta))/(mr^(2)) \dot{r} = \frac{p_r}{m}, \quad \dot{\theta} = \frac{p_\theta}{m r^2} r ˙ = p r m , θ ˙ = p θ m r 2
Substitute these into
H
H
H H H :
H
=
p
r
(
p
r
m
)
+
p
θ
(
p
θ
m
r
2
)
−
[
1
2
m
(
(
p
r
m
)
2
+
r
2
(
p
θ
m
r
2
)
2
)
−
G
M
m
(
1
2
a
−
1
r
)
]
H
=
p
r
p
r
m
+
p
θ
p
θ
m
r
2
−
1
2
m
p
r
m
2
+
r
2
p
θ
m
r
2
2
−
G
M
m
1
2
a
−
1
r
H=p_(r)((p_(r))/(m))+p_( theta)((p_( theta))/(mr^(2)))-[(1)/(2)m(((p_(r))/(m))^(2)+r^(2)((p_( theta))/(mr^(2)))^(2))-GMm((1)/(2a)-(1)/(r))] H = p_r \left( \frac{p_r}{m} \right) + p_\theta \left( \frac{p_\theta}{m r^2} \right) – \left[ \frac{1}{2} m \left( \left( \frac{p_r}{m} \right)^2 + r^2 \left( \frac{p_\theta}{m r^2} \right)^2 \right) – G M m \left( \frac{1}{2a} – \frac{1}{r} \right) \right] H = p r ( p r m ) + p θ ( p θ m r 2 ) − [ 1 2 m ( ( p r m ) 2 + r 2 ( p θ m r 2 ) 2 ) − G M m ( 1 2 a − 1 r ) ]
Simplify:
H
=
p
r
2
m
+
p
θ
2
m
r
2
−
[
p
r
2
2
m
+
p
θ
2
2
m
r
2
−
G
M
m
(
1
2
a
−
1
r
)
]
H
=
p
r
2
m
+
p
θ
2
m
r
2
−
p
r
2
2
m
+
p
θ
2
2
m
r
2
−
G
M
m
1
2
a
−
1
r
H=(p_(r)^(2))/(m)+(p_( theta)^(2))/(mr^(2))-[(p_(r)^(2))/(2m)+(p_( theta)^(2))/(2mr^(2))-GMm((1)/(2a)-(1)/(r))] H = \frac{p_r^2}{m} + \frac{p_\theta^2}{m r^2} – \left[ \frac{p_r^2}{2m} + \frac{p_\theta^2}{2m r^2} – G M m \left( \frac{1}{2a} – \frac{1}{r} \right) \right] H = p r 2 m + p θ 2 m r 2 − [ p r 2 2 m + p θ 2 2 m r 2 − G M m ( 1 2 a − 1 r ) ]
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
(
1
2
a
−
1
r
)
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
1
2
a
−
1
r
H=(p_(r)^(2))/(2m)+(p_( theta)^(2))/(2mr^(2))+GMm((1)/(2a)-(1)/(r)) H = \frac{p_r^2}{2m} + \frac{p_\theta^2}{2m r^2} + G M m \left( \frac{1}{2a} – \frac{1}{r} \right) H = p r 2 2 m + p θ 2 2 m r 2 + G M m ( 1 2 a − 1 r )
4. Hamilton’s Equations
Hamilton’s equations are given by:
q
˙
i
=
∂
H
∂
p
i
,
p
˙
i
=
−
∂
H
∂
q
i
q
˙
i
=
∂
H
∂
p
i
,
p
˙
i
=
−
∂
H
∂
q
i
q^(˙)_(i)=(del H)/(delp_(i)),quadp^(˙)_(i)=-(del H)/(delq_(i)) \dot{q}_i = \frac{\partial H}{\partial p_i}, \quad \dot{p}_i = -\frac{\partial H}{\partial q_i} q ˙ i = ∂ H ∂ p i , p ˙ i = − ∂ H ∂ q i
(a) For
r
r
r r r and
p
r
p
r
p_(r) p_r p r :
r
˙
=
∂
H
∂
p
r
=
p
r
m
r
˙
=
∂
H
∂
p
r
=
p
r
m
r^(˙)=(del H)/(delp_(r))=(p_(r))/(m) \dot{r} = \frac{\partial H}{\partial p_r} = \frac{p_r}{m} r ˙ = ∂ H ∂ p r = p r m
p
˙
r
=
−
∂
H
∂
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
p
˙
r
=
−
∂
H
∂
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
p^(˙)_(r)=-(del H)/(del r)=(p_( theta)^(2))/(mr^(3))-(GMm)/(r^(2)) \dot{p}_r = -\frac{\partial H}{\partial r} = \frac{p_\theta^2}{m r^3} – \frac{G M m}{r^2} p ˙ r = − ∂ H ∂ r = p θ 2 m r 3 − G M m r 2
(b) For
θ
θ
theta \theta θ and
p
θ
p
θ
p_( theta) p_\theta p θ :
θ
˙
=
∂
H
∂
p
θ
=
p
θ
m
r
2
θ
˙
=
∂
H
∂
p
θ
=
p
θ
m
r
2
theta^(˙)=(del H)/(delp_( theta))=(p_( theta))/(mr^(2)) \dot{\theta} = \frac{\partial H}{\partial p_\theta} = \frac{p_\theta}{m r^2} θ ˙ = ∂ H ∂ p θ = p θ m r 2
p
˙
θ
=
−
∂
H
∂
θ
=
0
(
since
H
does not depend on
θ
)
p
˙
θ
=
−
∂
H
∂
θ
=
0
(
since
H
does not depend on
θ
)
p^(˙)_(theta)=-(del H)/(del theta)=0quad(“since “H” does not depend on “theta) \dot{p}_\theta = -\frac{\partial H}{\partial \theta} = 0 \quad (\text{since \( H \) does not depend on \( \theta \)}) p ˙ θ = − ∂ H ∂ θ = 0 ( since H does not depend on θ )
Final Answer:
Hamiltonian:
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
(
1
2
a
−
1
r
)
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
1
2
a
−
1
r
H=(p_(r)^(2))/(2m)+(p_( theta)^(2))/(2mr^(2))+GMm((1)/(2a)-(1)/(r)) H = \frac{p_r^2}{2m} + \frac{p_\theta^2}{2m r^2} + G M m \left( \frac{1}{2a} – \frac{1}{r} \right) H = p r 2 2 m + p θ 2 2 m r 2 + G M m ( 1 2 a − 1 r )
Hamilton’s Equations:
{
r
˙
=
p
r
m
,
p
˙
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
,
θ
˙
=
p
θ
m
r
2
,
p
˙
θ
=
0
(
angular momentum is conserved
)
.
r
˙
=
p
r
m
,
p
˙
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
,
θ
˙
=
p
θ
m
r
2
,
p
˙
θ
=
0
(
angular momentum is conserved
)
.
{[r^(˙)=(p_(r))/(m)”,”],[p^(˙)_(r)=(p_( theta)^(2))/(mr^(3))-(GMm)/(r^(2))”,”],[theta^(˙)=(p_( theta))/(mr^(2))”,”],[p^(˙)_(theta)=0quad(“angular momentum is conserved”).]:} \begin{cases}
\dot{r} = \dfrac{p_r}{m}, \\
\dot{p}_r = \dfrac{p_\theta^2}{m r^3} – \dfrac{G M m}{r^2}, \\
\dot{\theta} = \dfrac{p_\theta}{m r^2}, \\
\dot{p}_\theta = 0 \quad (\text{angular momentum is conserved}).
\end{cases} { r ˙ = p r m , p ˙ r = p θ 2 m r 3 − G M m r 2 , θ ˙ = p θ m r 2 , p ˙ θ = 0 ( angular momentum is conserved ) .
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
(
1
2
a
−
1
r
)
,
r
˙
=
p
r
m
,
p
˙
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
,
θ
˙
=
p
θ
m
r
2
,
p
˙
θ
=
0.
H
=
p
r
2
2
m
+
p
θ
2
2
m
r
2
+
G
M
m
1
2
a
−
1
r
,
r
˙
=
p
r
m
,
p
˙
r
=
p
θ
2
m
r
3
−
G
M
m
r
2
,
θ
˙
=
p
θ
m
r
2
,
p
˙
θ
=
0.
[H=(p_(r)^(2))/(2m)+(p_( theta)^(2))/(2mr^(2))+GMm((1)/(2a)-(1)/(r))”,”],[r^(˙)=(p_(r))/(m)”,”],[p^(˙)_(r)=(p_( theta)^(2))/(mr^(3))-(GMm)/(r^(2))”,”],[theta^(˙)=(p_( theta))/(mr^(2))”,”],[p^(˙)_(theta)=0.] \boxed{
\begin{aligned}
H &= \frac{p_r^2}{2m} + \frac{p_\theta^2}{2m r^2} + G M m \left( \frac{1}{2a} – \frac{1}{r} \right), \\
\dot{r} &= \frac{p_r}{m}, \\
\dot{p}_r &= \frac{p_\theta^2}{m r^3} – \frac{G M m}{r^2}, \\
\dot{\theta} &= \frac{p_\theta}{m r^2}, \\
\dot{p}_\theta &= 0.
\end{aligned}
} H = p r 2 2 m + p θ 2 2 m r 2 + G M m ( 1 2 a − 1 r ) , r ˙ = p r m , p ˙ r = p θ 2 m r 3 − G M m r 2 , θ ˙ = p θ m r 2 , p ˙ θ = 0.
Question:-05 (e)
In a fluid motion, there is a source of strength
2
m
2
m
2m 2m 2 m placed at
z
=
2
z
=
2
z=2 z = 2 z = 2 and two sinks of strength
m
m
m m m placed at
z
=
2
+
i
z
=
2
+
i
z=2+i z = 2 + i z = 2 + i and
z
=
2
−
i
z
=
2
−
i
z=2-i z = 2 – i z = 2 − i . Find the streamlines.
Answer:
The streamlines of a fluid flow are described by the imaginary part of the complex potential function,
w
(
z
)
w
(
z
)
w(z) w(z) w ( z ) , being constant. For a system of sources and sinks, the total complex potential is the sum of the individual complex potentials.
1. The Complex Potential
The complex potential,
w
(
z
)
w
(
z
)
w(z) w(z) w ( z ) , for the given configuration is determined by summing the potentials from the source and the two sinks.
A source of strength
k
k
k k k at
z
0
z
0
z_(0) z_0 z 0 has a complex potential
k
ln
(
z
−
z
0
)
k
ln
(
z
−
z
0
)
k ln(z-z_(0)) k \ln(z – z_0) k ln ( z − z 0 ) .
A sink of strength
k
k
k k k at
z
0
z
0
z_(0) z_0 z 0 has a complex potential
−
k
ln
(
z
−
z
0
)
−
k
ln
(
z
−
z
0
)
-k ln(z-z_(0)) -k \ln(z – z_0) − k ln ( z − z 0 ) .
Given:
Source of strength
2
m
2
m
2m 2m 2 m at
z
=
2
z
=
2
z=2 z = 2 z = 2 .
Sink of strength
m
m
m m m at
z
=
2
+
i
z
=
2
+
i
z=2+i z = 2 + i z = 2 + i .
Sink of strength
m
m
m m m at
z
=
2
−
i
z
=
2
−
i
z=2-i z = 2 – i z = 2 − i .
The total complex potential
w
(
z
)
w
(
z
)
w(z) w(z) w ( z ) is:
w
(
z
)
=
2
m
ln
(
z
−
2
)
−
m
ln
(
z
−
(
2
+
i
)
)
−
m
ln
(
z
−
(
2
−
i
)
)
w
(
z
)
=
2
m
ln
(
z
−
2
)
−
m
ln
(
z
−
(
2
+
i
)
)
−
m
ln
(
z
−
(
2
−
i
)
)
w(z)=2m ln(z-2)-m ln(z-(2+i))-m ln(z-(2-i)) w(z) = 2m \ln(z – 2) – m \ln(z – (2 + i)) – m \ln(z – (2 – i)) w ( z ) = 2 m ln ( z − 2 ) − m ln ( z − ( 2 + i ) ) − m ln ( z − ( 2 − i ) )
Using the properties of logarithms, we can combine these terms:
w
(
z
)
=
m
[
2
ln
(
z
−
2
)
−
ln
(
z
−
2
−
i
)
−
ln
(
z
−
2
+
i
)
]
w
(
z
)
=
m
[
2
ln
(
z
−
2
)
−
ln
(
z
−
2
−
i
)
−
ln
(
z
−
2
+
i
)
]
w(z)=m[2ln(z-2)-ln(z-2-i)-ln(z-2+i)] w(z) = m [2 \ln(z – 2) – \ln(z – 2 – i) – \ln(z – 2 + i)] w ( z ) = m [ 2 ln ( z − 2 ) − ln ( z − 2 − i ) − ln ( z − 2 + i ) ]
w
(
z
)
=
m
[
ln
(
(
z
−
2
)
2
)
−
ln
(
(
z
−
2
−
i
)
(
z
−
2
+
i
)
)
]
w
(
z
)
=
m
[
ln
(
(
z
−
2
)
2
)
−
ln
(
(
z
−
2
−
i
)
(
z
−
2
+
i
)
)
]
w(z)=m[ln((z-2)^(2))-ln((z-2-i)(z-2+i))] w(z) = m [\ln((z – 2)^2) – \ln((z – 2 – i)(z – 2 + i))] w ( z ) = m [ ln ( ( z − 2 ) 2 ) − ln ( ( z − 2 − i ) ( z − 2 + i ) ) ]
w
(
z
)
=
m
ln
(
(
z
−
2
)
2
(
z
−
2
)
2
−
i
2
)
w
(
z
)
=
m
ln
(
z
−
2
)
2
(
z
−
2
)
2
−
i
2
w(z)=m ln(((z-2)^(2))/((z-2)^(2)-i^(2))) w(z) = m \ln\left(\frac{(z – 2)^2}{(z – 2)^2 – i^2}\right) w ( z ) = m ln ( ( z − 2 ) 2 ( z − 2 ) 2 − i 2 )
w
(
z
)
=
m
ln
(
(
z
−
2
)
2
(
z
−
2
)
2
+
1
)
w
(
z
)
=
m
ln
(
z
−
2
)
2
(
z
−
2
)
2
+
1
w(z)=m ln(((z-2)^(2))/((z-2)^(2)+1)) w(z) = m \ln\left(\frac{(z – 2)^2}{(z – 2)^2 + 1}\right) w ( z ) = m ln ( ( z − 2 ) 2 ( z − 2 ) 2 + 1 )
2. The Stream Function
The streamlines are given by the curves where the stream function,
ψ
(
x
,
y
)
=
Im
(
w
(
z
)
)
ψ
(
x
,
y
)
=
Im
(
w
(
z
)
)
psi(x,y)=”Im”(w(z)) \psi(x, y) = \text{Im}(w(z)) ψ ( x , y ) = Im ( w ( z ) ) , is constant. Let
z
=
x
+
i
y
z
=
x
+
i
y
z=x+iy z = x + iy z = x + i y .
The stream function
ψ
ψ
psi \psi ψ is the imaginary part of the complex potential:
ψ
=
Im
[
w
(
z
)
]
=
Im
[
2
m
ln
(
z
−
2
)
−
m
ln
(
z
−
2
−
i
)
−
m
ln
(
z
−
2
+
i
)
]
ψ
=
Im
[
w
(
z
)
]
=
Im
[
2
m
ln
(
z
−
2
)
−
m
ln
(
z
−
2
−
i
)
−
m
ln
(
z
−
2
+
i
)
]
psi=”Im”[w(z)]=”Im”[2m ln(z-2)-m ln(z-2-i)-m ln(z-2+i)] \psi = \text{Im}[w(z)] = \text{Im}[2m \ln(z-2) – m \ln(z-2-i) – m \ln(z-2+i)] ψ = Im [ w ( z ) ] = Im [ 2 m ln ( z − 2 ) − m ln ( z − 2 − i ) − m ln ( z − 2 + i ) ]
Since
Im
(
ln
(
ζ
)
)
=
arg
(
ζ
)
Im
(
ln
(
ζ
)
)
=
arg
(
ζ
)
“Im”(ln(zeta))=arg(zeta) \text{Im}(\ln(\zeta)) = \arg(\zeta) Im ( ln ( ζ ) ) = arg ( ζ ) , we have:
ψ
=
2
m
arg
(
z
−
2
)
−
m
arg
(
z
−
2
−
i
)
−
m
arg
(
z
−
2
+
i
)
ψ
=
2
m
arg
(
z
−
2
)
−
m
arg
(
z
−
2
−
i
)
−
m
arg
(
z
−
2
+
i
)
psi=2m arg(z-2)-m arg(z-2-i)-m arg(z-2+i) \psi = 2m \arg(z-2) – m \arg(z-2-i) – m \arg(z-2+i) ψ = 2 m arg ( z − 2 ) − m arg ( z − 2 − i ) − m arg ( z − 2 + i )
Let’s define the angles:
θ
1
=
arg
(
z
−
2
)
=
arg
(
(
x
−
2
)
+
i
y
)
=
arctan
(
y
x
−
2
)
θ
1
=
arg
(
z
−
2
)
=
arg
(
(
x
−
2
)
+
i
y
)
=
arctan
y
x
−
2
theta_(1)=arg(z-2)=arg((x-2)+iy)=arctan((y)/(x-2)) \theta_1 = \arg(z-2) = \arg((x-2) + iy) = \arctan\left(\frac{y}{x-2}\right) θ 1 = arg ( z − 2 ) = arg ( ( x − 2 ) + i y ) = arctan ( y x − 2 )
θ
2
=
arg
(
z
−
2
−
i
)
=
arg
(
(
x
−
2
)
+
i
(
y
−
1
)
)
=
arctan
(
y
−
1
x
−
2
)
θ
2
=
arg
(
z
−
2
−
i
)
=
arg
(
(
x
−
2
)
+
i
(
y
−
1
)
)
=
arctan
y
−
1
x
−
2
theta_(2)=arg(z-2-i)=arg((x-2)+i(y-1))=arctan((y-1)/(x-2)) \theta_2 = \arg(z-2-i) = \arg((x-2) + i(y-1)) = \arctan\left(\frac{y-1}{x-2}\right) θ 2 = arg ( z − 2 − i ) = arg ( ( x − 2 ) + i ( y − 1 ) ) = arctan ( y − 1 x − 2 )
θ
3
=
arg
(
z
−
2
+
i
)
=
arg
(
(
x
−
2
)
+
i
(
y
+
1
)
)
=
arctan
(
y
+
1
x
−
2
)
θ
3
=
arg
(
z
−
2
+
i
)
=
arg
(
(
x
−
2
)
+
i
(
y
+
1
)
)
=
arctan
y
+
1
x
−
2
theta_(3)=arg(z-2+i)=arg((x-2)+i(y+1))=arctan((y+1)/(x-2)) \theta_3 = \arg(z-2+i) = \arg((x-2) + i(y+1)) = \arctan\left(\frac{y+1}{x-2}\right) θ 3 = arg ( z − 2 + i ) = arg ( ( x − 2 ) + i ( y + 1 ) ) = arctan ( y + 1 x − 2 )
The equation for the streamlines is
ψ
=
constant
ψ
=
constant
psi=”constant” \psi = \text{constant} ψ = constant , so:
2
θ
1
−
θ
2
−
θ
3
=
C
1
2
θ
1
−
θ
2
−
θ
3
=
C
1
2theta_(1)-theta_(2)-theta_(3)=C_(1) 2\theta_1 – \theta_2 – \theta_3 = C_1 2 θ 1 − θ 2 − θ 3 = C 1
where
C
1
C
1
C_(1) C_1 C 1 is a constant.
This can be written as:
2
arctan
(
y
x
−
2
)
−
[
arctan
(
y
−
1
x
−
2
)
+
arctan
(
y
+
1
x
−
2
)
]
=
C
1
2
arctan
y
x
−
2
−
arctan
y
−
1
x
−
2
+
arctan
y
+
1
x
−
2
=
C
1
2arctan((y)/(x-2))-[arctan((y-1)/(x-2))+arctan((y+1)/(x-2))]=C_(1) 2\arctan\left(\frac{y}{x-2}\right) – \left[ \arctan\left(\frac{y-1}{x-2}\right) + \arctan\left(\frac{y+1}{x-2}\right) \right] = C_1 2 arctan ( y x − 2 ) − [ arctan ( y − 1 x − 2 ) + arctan ( y + 1 x − 2 ) ] = C 1
3. Equation of the Streamlines
To find the Cartesian equation for the streamlines, we use the tangent addition and double angle formulas for arctangents. Let
u
=
x
−
2
u
=
x
−
2
u=x-2 u = x – 2 u = x − 2 .
Using the identity
2
arctan
(
A
)
=
arctan
(
2
A
1
−
A
2
)
2
arctan
(
A
)
=
arctan
2
A
1
−
A
2
2arctan(A)=arctan((2A)/(1-A^(2))) 2\arctan(A) = \arctan\left(\frac{2A}{1-A^2}\right) 2 arctan ( A ) = arctan ( 2 A 1 − A 2 ) :
2
arctan
(
y
u
)
=
arctan
(
2
y
/
u
1
−
(
y
/
u
)
2
)
=
arctan
(
2
y
u
u
2
−
y
2
)
2
arctan
y
u
=
arctan
2
y
/
u
1
−
(
y
/
u
)
2
=
arctan
2
y
u
u
2
−
y
2
2arctan((y)/(u))=arctan((2y//u)/(1-(y//u)^(2)))=arctan((2yu)/(u^(2)-y^(2))) 2\arctan\left(\frac{y}{u}\right) = \arctan\left(\frac{2y/u}{1 – (y/u)^2}\right) = \arctan\left(\frac{2yu}{u^2 – y^2}\right) 2 arctan ( y u ) = arctan ( 2 y / u 1 − ( y / u ) 2 ) = arctan ( 2 y u u 2 − y 2 )
Using the identity
arctan
(
B
)
+
arctan
(
D
)
=
arctan
(
B
+
D
1
−
B
D
)
arctan
(
B
)
+
arctan
(
D
)
=
arctan
B
+
D
1
−
B
D
arctan(B)+arctan(D)=arctan((B+D)/(1-BD)) \arctan(B) + \arctan(D) = \arctan\left(\frac{B+D}{1-BD}\right) arctan ( B ) + arctan ( D ) = arctan ( B + D 1 − B D ) :
arctan
(
y
−
1
u
)
+
arctan
(
y
+
1
u
)
=
arctan
(
y
−
1
u
+
y
+
1
u
1
−
(
y
−
1
)
(
y
+
1
)
u
2
)
=
arctan
(
2
y
u
u
2
−
y
2
+
1
)
arctan
y
−
1
u
+
arctan
y
+
1
u
=
arctan
y
−
1
u
+
y
+
1
u
1
−
(
y
−
1
)
(
y
+
1
)
u
2
=
arctan
2
y
u
u
2
−
y
2
+
1
arctan((y-1)/(u))+arctan((y+1)/(u))=arctan(((y-1)/(u)+(y+1)/(u))/(1-((y-1)(y+1))/(u^(2))))=arctan((2yu)/(u^(2)-y^(2)+1)) \arctan\left(\frac{y-1}{u}\right) + \arctan\left(\frac{y+1}{u}\right) = \arctan\left(\frac{\frac{y-1}{u} + \frac{y+1}{u}}{1 – \frac{(y-1)(y+1)}{u^2}}\right) = \arctan\left(\frac{2yu}{u^2 – y^2 + 1}\right) arctan ( y − 1 u ) + arctan ( y + 1 u ) = arctan ( y − 1 u + y + 1 u 1 − ( y − 1 ) ( y + 1 ) u 2 ) = arctan ( 2 y u u 2 − y 2 + 1 )
Substituting these into the streamline equation gives:
arctan
(
2
y
u
u
2
−
y
2
)
−
arctan
(
2
y
u
u
2
−
y
2
+
1
)
=
C
1
arctan
2
y
u
u
2
−
y
2
−
arctan
2
y
u
u
2
−
y
2
+
1
=
C
1
arctan((2yu)/(u^(2)-y^(2)))-arctan((2yu)/(u^(2)-y^(2)+1))=C_(1) \arctan\left(\frac{2yu}{u^2 – y^2}\right) – \arctan\left(\frac{2yu}{u^2 – y^2 + 1}\right) = C_1 arctan ( 2 y u u 2 − y 2 ) − arctan ( 2 y u u 2 − y 2 + 1 ) = C 1
Taking the tangent of both sides and using the identity
tan
(
A
−
B
)
=
tan
A
−
tan
B
1
+
tan
A
tan
B
tan
(
A
−
B
)
=
tan
A
−
tan
B
1
+
tan
A
tan
B
tan(A-B)=(tan A-tan B)/(1+tan A tan B) \tan(A-B) = \frac{\tan A – \tan B}{1 + \tan A \tan B} tan ( A − B ) = tan A − tan B 1 + tan A tan B :
tan
(
C
1
)
=
2
y
u
u
2
−
y
2
−
2
y
u
u
2
−
y
2
+
1
1
+
(
2
y
u
u
2
−
y
2
)
(
2
y
u
u
2
−
y
2
+
1
)
tan
(
C
1
)
=
2
y
u
u
2
−
y
2
−
2
y
u
u
2
−
y
2
+
1
1
+
2
y
u
u
2
−
y
2
2
y
u
u
2
−
y
2
+
1
tan(C_(1))=((2yu)/(u^(2)-y^(2))-(2yu)/(u^(2)-y^(2)+1))/(1+((2yu)/(u^(2)-y^(2)))((2yu)/(u^(2)-y^(2)+1))) \tan(C_1) = \frac{\frac{2yu}{u^2 – y^2} – \frac{2yu}{u^2 – y^2 + 1}}{1 + \left(\frac{2yu}{u^2 – y^2}\right)\left(\frac{2yu}{u^2 – y^2 + 1}\right)} tan ( C 1 ) = 2 y u u 2 − y 2 − 2 y u u 2 − y 2 + 1 1 + ( 2 y u u 2 − y 2 ) ( 2 y u u 2 − y 2 + 1 )
Let
C
=
tan
(
C
1
)
C
=
tan
(
C
1
)
C=tan(C_(1)) C = \tan(C_1) C = tan ( C 1 ) . Simplifying the expression gives:
C
=
2
y
u
(
(
u
2
−
y
2
+
1
)
−
(
u
2
−
y
2
)
)
(
u
2
−
y
2
)
(
u
2
−
y
2
+
1
)
+
(
2
y
u
)
2
C
=
2
y
u
(
(
u
2
−
y
2
+
1
)
−
(
u
2
−
y
2
)
)
(
u
2
−
y
2
)
(
u
2
−
y
2
+
1
)
+
(
2
y
u
)
2
C=(2yu((u^(2)-y^(2)+1)-(u^(2)-y^(2))))/((u^(2)-y^(2))(u^(2)-y^(2)+1)+(2yu)^(2)) C = \frac{2yu((u^2 – y^2 + 1) – (u^2 – y^2))}{(u^2 – y^2)(u^2 – y^2 + 1) + (2yu)^2} C = 2 y u ( ( u 2 − y 2 + 1 ) − ( u 2 − y 2 ) ) ( u 2 − y 2 ) ( u 2 − y 2 + 1 ) + ( 2 y u ) 2
C
=
2
y
u
(
u
2
−
y
2
)
2
+
(
u
2
−
y
2
)
+
4
u
2
y
2
C
=
2
y
u
(
u
2
−
y
2
)
2
+
(
u
2
−
y
2
)
+
4
u
2
y
2
C=(2yu)/((u^(2)-y^(2))^(2)+(u^(2)-y^(2))+4u^(2)y^(2)) C = \frac{2yu}{(u^2 – y^2)^2 + (u^2 – y^2) + 4u^2y^2} C = 2 y u ( u 2 − y 2 ) 2 + ( u 2 − y 2 ) + 4 u 2 y 2
C
=
2
y
u
u
4
−
2
u
2
y
2
+
y
4
+
u
2
−
y
2
+
4
u
2
y
2
C
=
2
y
u
u
4
−
2
u
2
y
2
+
y
4
+
u
2
−
y
2
+
4
u
2
y
2
C=(2yu)/(u^(4)-2u^(2)y^(2)+y^(4)+u^(2)-y^(2)+4u^(2)y^(2)) C = \frac{2yu}{u^4 – 2u^2y^2 + y^4 + u^2 – y^2 + 4u^2y^2} C = 2 y u u 4 − 2 u 2 y 2 + y 4 + u 2 − y 2 + 4 u 2 y 2
C
=
2
y
u
u
4
+
2
u
2
y
2
+
y
4
+
u
2
−
y
2
C
=
2
y
u
u
4
+
2
u
2
y
2
+
y
4
+
u
2
−
y
2
C=(2yu)/(u^(4)+2u^(2)y^(2)+y^(4)+u^(2)-y^(2)) C = \frac{2yu}{u^4 + 2u^2y^2 + y^4 + u^2 – y^2} C = 2 y u u 4 + 2 u 2 y 2 + y 4 + u 2 − y 2
C
=
2
y
u
(
u
2
+
y
2
)
2
+
u
2
−
y
2
C
=
2
y
u
(
u
2
+
y
2
)
2
+
u
2
−
y
2
C=(2yu)/((u^(2)+y^(2))^(2)+u^(2)-y^(2)) C = \frac{2yu}{(u^2 + y^2)^2 + u^2 – y^2} C = 2 y u ( u 2 + y 2 ) 2 + u 2 − y 2
Substituting back
u
=
x
−
2
u
=
x
−
2
u=x-2 u = x – 2 u = x − 2 , the family of streamlines is given by the equation:
C
=
2
y
(
x
−
2
)
(
(
x
−
2
)
2
+
y
2
)
2
+
(
x
−
2
)
2
−
y
2
C
=
2
y
(
x
−
2
)
(
(
x
−
2
)
2
+
y
2
)
2
+
(
x
−
2
)
2
−
y
2
C=(2y(x-2))/(((x-2)^(2)+y^(2))^(2)+(x-2)^(2)-y^(2)) C = \frac{2y(x-2)}{((x-2)^2 + y^2)^2 + (x-2)^2 – y^2} C = 2 y ( x − 2 ) ( ( x − 2 ) 2 + y 2 ) 2 + ( x − 2 ) 2 − y 2
where
C
C
C C C is an arbitrary constant defining each streamline. This can be rewritten as:
C
[
(
(
x
−
2
)
2
+
y
2
)
2
+
(
x
−
2
)
2
−
y
2
]
=
2
y
(
x
−
2
)
C
(
(
x
−
2
)
2
+
y
2
)
2
+
(
x
−
2
)
2
−
y
2
=
2
y
(
x
−
2
)
C[((x-2)^(2)+y^(2))^(2)+(x-2)^(2)-y^(2)]=2y(x-2) C \left[ ((x-2)^2 + y^2)^2 + (x-2)^2 – y^2 \right] = 2y(x-2) C [ ( ( x − 2 ) 2 + y 2 ) 2 + ( x − 2 ) 2 − y 2 ] = 2 y ( x − 2 )
Question:-06
(a) Find the surface passing through the two lines
z
=
x
=
0
z
=
x
=
0
z=x=0 z = x = 0 z = x = 0 and
z
−
1
=
x
−
y
=
0
z
−
1
=
x
−
y
=
0
z-1=x-y=0 z – 1 = x – y = 0 z − 1 = x − y = 0 , and satisfying the partial differential equation
∂
2
z
∂
x
2
−
4
∂
2
z
∂
x
∂
y
+
4
∂
2
z
∂
y
2
=
0
∂
2
z
∂
x
2
−
4
∂
2
z
∂
x
∂
y
+
4
∂
2
z
∂
y
2
=
0
(del^(2)z)/(delx^(2))-4(del^(2)z)/(del x del y)+4(del^(2)z)/(dely^(2))=0 \frac{\partial^2 z}{\partial x^2} – 4 \frac{\partial^2 z}{\partial x \partial y} + 4 \frac{\partial^2 z}{\partial y^2} = 0 ∂ 2 z ∂ x 2 − 4 ∂ 2 z ∂ x ∂ y + 4 ∂ 2 z ∂ y 2 = 0 .
Answer:
To find the surface
z
=
f
(
x
,
y
)
z
=
f
(
x
,
y
)
z=f(x,y) z = f(x, y) z = f ( x , y ) passing through the two given lines and satisfying the given partial differential equation (PDE), we proceed step-by-step.
Given:
Lines:
L
1
:
z
=
x
=
0
L
1
:
z
=
x
=
0
L_(1):z=x=0 L_1: z = x = 0 L 1 : z = x = 0 (the
y
y
y y y -axis),
L
2
:
z
−
1
=
x
−
y
=
0
L
2
:
z
−
1
=
x
−
y
=
0
L_(2):z-1=x-y=0 L_2: z – 1 = x – y = 0 L 2 : z − 1 = x − y = 0 (the line
x
=
y
x
=
y
x=y x = y x = y at height
z
=
1
z
=
1
z=1 z = 1 z = 1 ).
PDE:
∂
2
z
∂
x
2
−
4
∂
2
z
∂
x
∂
y
+
4
∂
2
z
∂
y
2
=
0.
∂
2
z
∂
x
2
−
4
∂
2
z
∂
x
∂
y
+
4
∂
2
z
∂
y
2
=
0.
(del^(2)z)/(delx^(2))-4(del^(2)z)/(del x del y)+4(del^(2)z)/(dely^(2))=0. \frac{\partial^2 z}{\partial x^2} – 4 \frac{\partial^2 z}{\partial x \partial y} + 4 \frac{\partial^2 z}{\partial y^2} = 0. ∂ 2 z ∂ x 2 − 4 ∂ 2 z ∂ x ∂ y + 4 ∂ 2 z ∂ y 2 = 0.
Step 1: Solve the PDE
The given PDE is a second-order linear homogeneous PDE with constant coefficients:
z
x
x
−
4
z
x
y
+
4
z
y
y
=
0.
z
x
x
−
4
z
x
y
+
4
z
y
y
=
0.
z_(xx)-4z_(xy)+4z_(yy)=0. z_{xx} – 4 z_{xy} + 4 z_{yy} = 0. z x x − 4 z x y + 4 z y y = 0.
We can solve it using the method of characteristics or by assuming a solution of the form
z
=
f
(
a
x
+
b
y
)
z
=
f
(
a
x
+
b
y
)
z=f(ax+by) z = f(ax + by) z = f ( a x + b y ) .
Let’s rewrite the PDE in terms of the differential operator:
(
∂
2
∂
x
2
−
4
∂
2
∂
x
∂
y
+
4
∂
2
∂
y
2
)
z
=
0.
∂
2
∂
x
2
−
4
∂
2
∂
x
∂
y
+
4
∂
2
∂
y
2
z
=
0.
((del^(2))/(delx^(2))-4(del^(2))/(del x del y)+4(del^(2))/(dely^(2)))z=0. \left( \frac{\partial^2}{\partial x^2} – 4 \frac{\partial^2}{\partial x \partial y} + 4 \frac{\partial^2}{\partial y^2} \right) z = 0. ( ∂ 2 ∂ x 2 − 4 ∂ 2 ∂ x ∂ y + 4 ∂ 2 ∂ y 2 ) z = 0.
The characteristic equation is obtained by replacing
∂
x
∂
x
del _(x) \partial_x ∂ x with
m
m
m m m and
∂
y
∂
y
del _(y) \partial_y ∂ y with
1
1
1 1 1 :
m
2
−
4
m
+
4
=
0
⟹
(
m
−
2
)
2
=
0
⟹
m
=
2
(double root)
.
m
2
−
4
m
+
4
=
0
⟹
(
m
−
2
)
2
=
0
⟹
m
=
2
(double root)
.
m^(2)-4m+4=0Longrightarrow(m-2)^(2)=0Longrightarrowm=2″ (double root)”. m^2 – 4m + 4 = 0 \implies (m – 2)^2 = 0 \implies m = 2 \text{ (double root)}. m 2 − 4 m + 4 = 0 ⟹ ( m − 2 ) 2 = 0 ⟹ m = 2 (double root) .
Thus, the general solution is:
z
(
x
,
y
)
=
f
(
y
+
2
x
)
+
x
g
(
y
+
2
x
)
,
z
(
x
,
y
)
=
f
(
y
+
2
x
)
+
x
g
(
y
+
2
x
)
,
z(x,y)=f(y+2x)+xg(y+2x), z(x, y) = f(y + 2x) + x g(y + 2x), z ( x , y ) = f ( y + 2 x ) + x g ( y + 2 x ) ,
where
f
f
f f f and
g
g
g g g are arbitrary functions of
ξ
=
y
+
2
x
ξ
=
y
+
2
x
xi=y+2x \xi = y + 2x ξ = y + 2 x .
Step 2: Apply Boundary Conditions
We now impose the conditions that the surface passes through
L
1
L
1
L_(1) L_1 L 1 and
L
2
L
2
L_(2) L_2 L 2 .
On
L
1
L
1
L_(1) L_1 L 1 :
x
=
0
x
=
0
x=0 x = 0 x = 0 ,
z
=
0
z
=
0
z=0 z = 0 z = 0 .
Substituting
x
=
0
x
=
0
x=0 x = 0 x = 0 into the general solution:
z
(
0
,
y
)
=
f
(
y
)
+
0
⋅
g
(
y
)
=
f
(
y
)
=
0.
z
(
0
,
y
)
=
f
(
y
)
+
0
⋅
g
(
y
)
=
f
(
y
)
=
0.
z(0,y)=f(y)+0*g(y)=f(y)=0. z(0, y) = f(y) + 0 \cdot g(y) = f(y) = 0. z ( 0 , y ) = f ( y ) + 0 ⋅ g ( y ) = f ( y ) = 0.
Thus,
f
(
y
)
=
0
f
(
y
)
=
0
f(y)=0 f(y) = 0 f ( y ) = 0 , and the solution simplifies to:
z
(
x
,
y
)
=
x
g
(
y
+
2
x
)
.
z
(
x
,
y
)
=
x
g
(
y
+
2
x
)
.
z(x,y)=xg(y+2x). z(x, y) = x g(y + 2x). z ( x , y ) = x g ( y + 2 x ) .
On
L
2
L
2
L_(2) L_2 L 2 :
x
=
y
x
=
y
x=y x = y x = y ,
z
=
1
z
=
1
z=1 z = 1 z = 1 .
Substituting
x
=
y
x
=
y
x=y x = y x = y into the simplified solution:
z
(
y
,
y
)
=
y
g
(
y
+
2
y
)
=
y
g
(
3
y
)
=
1.
z
(
y
,
y
)
=
y
g
(
y
+
2
y
)
=
y
g
(
3
y
)
=
1.
z(y,y)=yg(y+2y)=yg(3y)=1. z(y, y) = y g(y + 2y) = y g(3y) = 1. z ( y , y ) = y g ( y + 2 y ) = y g ( 3 y ) = 1.
Thus,
g
(
3
y
)
=
1
y
g
(
3
y
)
=
1
y
g(3y)=(1)/(y) g(3y) = \frac{1}{y} g ( 3 y ) = 1 y . Let
ξ
=
3
y
ξ
=
3
y
xi=3y \xi = 3y ξ = 3 y , so
y
=
ξ
3
y
=
ξ
3
y=(xi)/(3) y = \frac{\xi}{3} y = ξ 3 , and:
g
(
ξ
)
=
3
ξ
.
g
(
ξ
)
=
3
ξ
.
g(xi)=(3)/(xi). g(\xi) = \frac{3}{\xi}. g ( ξ ) = 3 ξ .
Therefore,
g
(
y
+
2
x
)
=
3
y
+
2
x
g
(
y
+
2
x
)
=
3
y
+
2
x
g(y+2x)=(3)/(y+2x) g(y + 2x) = \frac{3}{y + 2x} g ( y + 2 x ) = 3 y + 2 x .
Step 3: Final Solution
Substituting
g
g
g g g back into the simplified solution:
z
(
x
,
y
)
=
x
⋅
3
y
+
2
x
=
3
x
2
x
+
y
.
z
(
x
,
y
)
=
x
⋅
3
y
+
2
x
=
3
x
2
x
+
y
.
z(x,y)=x*(3)/(y+2x)=(3x)/(2x+y). z(x, y) = x \cdot \frac{3}{y + 2x} = \frac{3x}{2x + y}. z ( x , y ) = x ⋅ 3 y + 2 x = 3 x 2 x + y .
Verification:
Check PDE:
Compute the second derivatives:
z
x
=
3
(
y
+
2
x
)
−
3
x
⋅
2
(
2
x
+
y
)
2
=
3
y
(
2
x
+
y
)
2
,
z
x
=
3
(
y
+
2
x
)
−
3
x
⋅
2
(
2
x
+
y
)
2
=
3
y
(
2
x
+
y
)
2
,
z_(x)=(3(y+2x)-3x*2)/((2x+y)^(2))=(3y)/((2x+y)^(2)), z_x = \frac{3(y + 2x) – 3x \cdot 2}{(2x + y)^2} = \frac{3y}{(2x + y)^2}, z x = 3 ( y + 2 x ) − 3 x ⋅ 2 ( 2 x + y ) 2 = 3 y ( 2 x + y ) 2 ,
z
x
x
=
−
6
y
⋅
2
(
2
x
+
y
)
3
=
−
12
y
(
2
x
+
y
)
3
,
z
x
x
=
−
6
y
⋅
2
(
2
x
+
y
)
3
=
−
12
y
(
2
x
+
y
)
3
,
z_(xx)=(-6y*2)/((2x+y)^(3))=(-12 y)/((2x+y)^(3)), z_{xx} = \frac{-6y \cdot 2}{(2x + y)^3} = \frac{-12y}{(2x + y)^3}, z x x = − 6 y ⋅ 2 ( 2 x + y ) 3 = − 12 y ( 2 x + y ) 3 ,
z
y
=
−
3
x
(
2
x
+
y
)
2
,
z
y
=
−
3
x
(
2
x
+
y
)
2
,
z_(y)=(-3x)/((2x+y)^(2)), z_y = \frac{-3x}{(2x + y)^2}, z y = − 3 x ( 2 x + y ) 2 ,
z
y
y
=
6
x
(
2
x
+
y
)
3
,
z
y
y
=
6
x
(
2
x
+
y
)
3
,
z_(yy)=(6x)/((2x+y)^(3)), z_{yy} = \frac{6x}{(2x + y)^3}, z y y = 6 x ( 2 x + y ) 3 ,
z
x
y
=
3
(
2
x
+
y
)
2
−
3
y
⋅
2
(
2
x
+
y
)
(
2
x
+
y
)
4
=
6
x
+
3
y
−
6
y
(
2
x
+
y
)
3
=
6
x
−
3
y
(
2
x
+
y
)
3
.
z
x
y
=
3
(
2
x
+
y
)
2
−
3
y
⋅
2
(
2
x
+
y
)
(
2
x
+
y
)
4
=
6
x
+
3
y
−
6
y
(
2
x
+
y
)
3
=
6
x
−
3
y
(
2
x
+
y
)
3
.
z_(xy)=(3(2x+y)^(2)-3y*2(2x+y))/((2x+y)^(4))=(6x+3y-6y)/((2x+y)^(3))=(6x-3y)/((2x+y)^(3)). z_{xy} = \frac{3(2x + y)^2 – 3y \cdot 2(2x + y)}{(2x + y)^4} = \frac{6x + 3y – 6y}{(2x + y)^3} = \frac{6x – 3y}{(2x + y)^3}. z x y = 3 ( 2 x + y ) 2 − 3 y ⋅ 2 ( 2 x + y ) ( 2 x + y ) 4 = 6 x + 3 y − 6 y ( 2 x + y ) 3 = 6 x − 3 y ( 2 x + y ) 3 .
Substituting into the PDE:
z
x
x
−
4
z
x
y
+
4
z
y
y
=
−
12
y
(
2
x
+
y
)
3
−
4
⋅
6
x
−
3
y
(
2
x
+
y
)
3
+
4
⋅
6
x
(
2
x
+
y
)
3
=
0.
z
x
x
−
4
z
x
y
+
4
z
y
y
=
−
12
y
(
2
x
+
y
)
3
−
4
⋅
6
x
−
3
y
(
2
x
+
y
)
3
+
4
⋅
6
x
(
2
x
+
y
)
3
=
0.
z_(xx)-4z_(xy)+4z_(yy)=(-12 y)/((2x+y)^(3))-4*(6x-3y)/((2x+y)^(3))+4*(6x)/((2x+y)^(3))=0. z_{xx} – 4 z_{xy} + 4 z_{yy} = \frac{-12y}{(2x + y)^3} – 4 \cdot \frac{6x – 3y}{(2x + y)^3} + 4 \cdot \frac{6x}{(2x + y)^3} = 0. z x x − 4 z x y + 4 z y y = − 12 y ( 2 x + y ) 3 − 4 ⋅ 6 x − 3 y ( 2 x + y ) 3 + 4 ⋅ 6 x ( 2 x + y ) 3 = 0.
Simplifying:
−
12
y
−
24
x
+
12
y
+
24
x
=
0.
−
12
y
−
24
x
+
12
y
+
24
x
=
0.
-12 y-24 x+12 y+24 x=0. -12y – 24x + 12y + 24x = 0. − 12 y − 24 x + 12 y + 24 x = 0.
The PDE is satisfied.
Check Boundary Conditions:
On
L
1
L
1
L_(1) L_1 L 1 :
x
=
0
x
=
0
x=0 x = 0 x = 0 ,
z
=
0
0
+
y
=
0
z
=
0
0
+
y
=
0
z=(0)/(0+y)=0 z = \frac{0}{0 + y} = 0 z = 0 0 + y = 0 .
On
L
2
L
2
L_(2) L_2 L 2 :
x
=
y
x
=
y
x=y x = y x = y ,
z
=
3
y
2
y
+
y
=
1
z
=
3
y
2
y
+
y
=
1
z=(3y)/(2y+y)=1 z = \frac{3y}{2y + y} = 1 z = 3 y 2 y + y = 1 .
Both conditions are satisfied.
Final Answer:
The required surface is:
z
=
3
x
2
x
+
y
.
z
=
3
x
2
x
+
y
.
z=(3x)/(2x+y). \boxed{z = \frac{3x}{2x + y}}. z = 3 x 2 x + y .
Question:-06 (b)
Solve the system of linear equations
7
x
1
−
x
2
+
2
x
3
=
11
2
x
1
+
8
x
2
−
x
3
=
9
x
1
−
2
x
2
+
9
x
3
=
7
7
x
1
−
x
2
+
2
x
3
=
11
2
x
1
+
8
x
2
−
x
3
=
9
x
1
−
2
x
2
+
9
x
3
=
7
{:[7x_(1)-x_(2)+2x_(3)=11],[2x_(1)+8x_(2)-x_(3)=9],[x_(1)-2x_(2)+9x_(3)=7]:} \begin{aligned}
7x_1 – x_2 + 2x_3 &= 11 \\
2x_1 + 8x_2 – x_3 &= 9 \\
x_1 – 2x_2 + 9x_3 &= 7
\end{aligned} 7 x 1 − x 2 + 2 x 3 = 11 2 x 1 + 8 x 2 − x 3 = 9 x 1 − 2 x 2 + 9 x 3 = 7
correct up to 4 significant figures by the Gauss-Seidel iterative method. Take the initially guessed solution as
x
1
=
x
2
=
x
3
=
0
x
1
=
x
2
=
x
3
=
0
x_(1)=x_(2)=x_(3)=0 x_1 = x_2 = x_3 = 0 x 1 = x 2 = x 3 = 0 .
Answer:
To solve the system of linear equations using the Gauss-Seidel iterative method with initial guesses
x
1
=
x
2
=
x
3
=
0
x
1
=
x
2
=
x
3
=
0
x_(1)=x_(2)=x_(3)=0 x_1 = x_2 = x_3 = 0 x 1 = x 2 = x 3 = 0 , we aim to find
x
1
,
x
2
,
x
3
x
1
,
x
2
,
x
3
x_(1),x_(2),x_(3) x_1, x_2, x_3 x 1 , x 2 , x 3 correct to 4 significant figures. The system is:
7
x
1
−
x
2
+
2
x
3
=
11
2
x
1
+
8
x
2
−
x
3
=
9
x
1
−
2
x
2
+
9
x
3
=
7
7
x
1
−
x
2
+
2
x
3
=
11
2
x
1
+
8
x
2
−
x
3
=
9
x
1
−
2
x
2
+
9
x
3
=
7
{:[7x_(1)-x_(2)+2x_(3)=11],[2x_(1)+8x_(2)-x_(3)=9],[x_(1)-2x_(2)+9x_(3)=7]:} \begin{aligned}
7x_1 – x_2 + 2x_3 &= 11 \\
2x_1 + 8x_2 – x_3 &= 9 \\
x_1 – 2x_2 + 9x_3 &= 7
\end{aligned} 7 x 1 − x 2 + 2 x 3 = 11 2 x 1 + 8 x 2 − x 3 = 9 x 1 − 2 x 2 + 9 x 3 = 7
Gauss-Seidel Method
The Gauss-Seidel method is an iterative technique for solving a system of linear equations
A
x
=
b
A
x
=
b
Ax=b Ax = b A x = b . It updates each variable using the most recent values available. First, we rewrite each equation to isolate each variable:
From
7
x
1
−
x
2
+
2
x
3
=
11
7
x
1
−
x
2
+
2
x
3
=
11
7x_(1)-x_(2)+2x_(3)=11 7x_1 – x_2 + 2x_3 = 11 7 x 1 − x 2 + 2 x 3 = 11 :
x
1
=
11
+
x
2
−
2
x
3
7
x
1
=
11
+
x
2
−
2
x
3
7
x_(1)=(11+x_(2)-2x_(3))/(7) x_1 = \frac{11 + x_2 – 2x_3}{7} x 1 = 11 + x 2 − 2 x 3 7
From
2
x
1
+
8
x
2
−
x
3
=
9
2
x
1
+
8
x
2
−
x
3
=
9
2x_(1)+8x_(2)-x_(3)=9 2x_1 + 8x_2 – x_3 = 9 2 x 1 + 8 x 2 − x 3 = 9 :
x
2
=
9
−
2
x
1
+
x
3
8
x
2
=
9
−
2
x
1
+
x
3
8
x_(2)=(9-2x_(1)+x_(3))/(8) x_2 = \frac{9 – 2x_1 + x_3}{8} x 2 = 9 − 2 x 1 + x 3 8
From
x
1
−
2
x
2
+
9
x
3
=
7
x
1
−
2
x
2
+
9
x
3
=
7
x_(1)-2x_(2)+9x_(3)=7 x_1 – 2x_2 + 9x_3 = 7 x 1 − 2 x 2 + 9 x 3 = 7 :
x
3
=
7
−
x
1
+
2
x
2
9
x
3
=
7
−
x
1
+
2
x
2
9
x_(3)=(7-x_(1)+2x_(2))/(9) x_3 = \frac{7 – x_1 + 2x_2}{9} x 3 = 7 − x 1 + 2 x 2 9
Starting with initial guesses
x
1
(
0
)
=
0
x
1
(
0
)
=
0
x_(1)^((0))=0 x_1^{(0)} = 0 x 1 ( 0 ) = 0 ,
x
2
(
0
)
=
0
x
2
(
0
)
=
0
x_(2)^((0))=0 x_2^{(0)} = 0 x 2 ( 0 ) = 0 ,
x
3
(
0
)
=
0
x
3
(
0
)
=
0
x_(3)^((0))=0 x_3^{(0)} = 0 x 3 ( 0 ) = 0 , we iterate by computing each variable in sequence, using the latest values for subsequent calculations. We continue until the values converge to 4 significant figures, i.e., the absolute difference between successive iterations for each variable is less than
0.00005
0.00005
0.00005 0.00005 0.00005 (since
0.00005
=
5
×
10
−
5
0.00005
=
5
×
10
−
5
0.00005=5xx10^(-5) 0.00005 = 5 \times 10^{-5} 0.00005 = 5 × 10 − 5 , ensuring 4 significant figures).
Iteration Process
We perform iterations, rounding intermediate results to 6 decimal places for precision during calculations, but report final answers to 4 significant figures as requested.
Iteration 1:
Compute
x
1
(
1
)
x
1
(
1
)
x_(1)^((1)) x_1^{(1)} x 1 ( 1 ) :
x
1
(
1
)
=
11
+
x
2
(
0
)
−
2
x
3
(
0
)
7
=
11
+
0
−
2
⋅
0
7
=
11
7
≈
1.571429
x
1
(
1
)
=
11
+
x
2
(
0
)
−
2
x
3
(
0
)
7
=
11
+
0
−
2
⋅
0
7
=
11
7
≈
1.571429
x_(1)^((1))=(11+x_(2)^((0))-2x_(3)^((0)))/(7)=(11+0-2*0)/(7)=(11)/(7)~~1.571429 x_1^{(1)} = \frac{11 + x_2^{(0)} – 2x_3^{(0)}}{7} = \frac{11 + 0 – 2 \cdot 0}{7} = \frac{11}{7} \approx 1.571429 x 1 ( 1 ) = 11 + x 2 ( 0 ) − 2 x 3 ( 0 ) 7 = 11 + 0 − 2 ⋅ 0 7 = 11 7 ≈ 1.571429
Compute
x
2
(
1
)
x
2
(
1
)
x_(2)^((1)) x_2^{(1)} x 2 ( 1 ) , using
x
1
(
1
)
x
1
(
1
)
x_(1)^((1)) x_1^{(1)} x 1 ( 1 ) :
x
2
(
1
)
=
9
−
2
x
1
(
1
)
+
x
3
(
0
)
8
=
9
−
2
⋅
1.571429
+
0
8
=
9
−
3.142858
8
=
5.857142
8
≈
0.732143
x
2
(
1
)
=
9
−
2
x
1
(
1
)
+
x
3
(
0
)
8
=
9
−
2
⋅
1.571429
+
0
8
=
9
−
3.142858
8
=
5.857142
8
≈
0.732143
x_(2)^((1))=(9-2x_(1)^((1))+x_(3)^((0)))/(8)=(9-2*1.571429+0)/(8)=(9-3.142858)/(8)=(5.857142)/(8)~~0.732143 x_2^{(1)} = \frac{9 – 2x_1^{(1)} + x_3^{(0)}}{8} = \frac{9 – 2 \cdot 1.571429 + 0}{8} = \frac{9 – 3.142858}{8} = \frac{5.857142}{8} \approx 0.732143 x 2 ( 1 ) = 9 − 2 x 1 ( 1 ) + x 3 ( 0 ) 8 = 9 − 2 ⋅ 1.571429 + 0 8 = 9 − 3.142858 8 = 5.857142 8 ≈ 0.732143
Compute
x
3
(
1
)
x
3
(
1
)
x_(3)^((1)) x_3^{(1)} x 3 ( 1 ) , using
x
1
(
1
)
x
1
(
1
)
x_(1)^((1)) x_1^{(1)} x 1 ( 1 ) ,
x
2
(
1
)
x
2
(
1
)
x_(2)^((1)) x_2^{(1)} x 2 ( 1 ) :
x
3
(
1
)
=
7
−
x
1
(
1
)
+
2
x
2
(
1
)
9
=
7
−
1.571429
+
2
⋅
0.732143
9
=
7
−
1.571429
+
1.464286
9
=
6.892857
9
≈
0.765873
x
3
(
1
)
=
7
−
x
1
(
1
)
+
2
x
2
(
1
)
9
=
7
−
1.571429
+
2
⋅
0.732143
9
=
7
−
1.571429
+
1.464286
9
=
6.892857
9
≈
0.765873
x_(3)^((1))=(7-x_(1)^((1))+2x_(2)^((1)))/(9)=(7-1.571429+2*0.732143)/(9)=(7-1.571429+1.464286)/(9)=(6.892857)/(9)~~0.765873 x_3^{(1)} = \frac{7 – x_1^{(1)} + 2x_2^{(1)}}{9} = \frac{7 – 1.571429 + 2 \cdot 0.732143}{9} = \frac{7 – 1.571429 + 1.464286}{9} = \frac{6.892857}{9} \approx 0.765873 x 3 ( 1 ) = 7 − x 1 ( 1 ) + 2 x 2 ( 1 ) 9 = 7 − 1.571429 + 2 ⋅ 0.732143 9 = 7 − 1.571429 + 1.464286 9 = 6.892857 9 ≈ 0.765873
Results after Iteration 1:
x
1
(
1
)
≈
1.571429
,
x
2
(
1
)
≈
0.732143
,
x
3
(
1
)
≈
0.765873
x
1
(
1
)
≈
1.571429
,
x
2
(
1
)
≈
0.732143
,
x
3
(
1
)
≈
0.765873
x_(1)^((1))~~1.571429,quadx_(2)^((1))~~0.732143,quadx_(3)^((1))~~0.765873 x_1^{(1)} \approx 1.571429, \quad x_2^{(1)} \approx 0.732143, \quad x_3^{(1)} \approx 0.765873 x 1 ( 1 ) ≈ 1.571429 , x 2 ( 1 ) ≈ 0.732143 , x 3 ( 1 ) ≈ 0.765873
Iteration 2:
Compute
x
1
(
2
)
x
1
(
2
)
x_(1)^((2)) x_1^{(2)} x 1 ( 2 ) :
x
1
(
2
)
=
11
+
x
2
(
1
)
−
2
x
3
(
1
)
7
=
11
+
0.732143
−
2
⋅
0.765873
7
=
11
+
0.732143
−
1.531746
7
=
10.200397
7
≈
1.457199
x
1
(
2
)
=
11
+
x
2
(
1
)
−
2
x
3
(
1
)
7
=
11
+
0.732143
−
2
⋅
0.765873
7
=
11
+
0.732143
−
1.531746
7
=
10.200397
7
≈
1.457199
x_(1)^((2))=(11+x_(2)^((1))-2x_(3)^((1)))/(7)=(11+0.732143-2*0.765873)/(7)=(11+0.732143-1.531746)/(7)=(10.200397)/(7)~~1.457199 x_1^{(2)} = \frac{11 + x_2^{(1)} – 2x_3^{(1)}}{7} = \frac{11 + 0.732143 – 2 \cdot 0.765873}{7} = \frac{11 + 0.732143 – 1.531746}{7} = \frac{10.200397}{7} \approx 1.457199 x 1 ( 2 ) = 11 + x 2 ( 1 ) − 2 x 3 ( 1 ) 7 = 11 + 0.732143 − 2 ⋅ 0.765873 7 = 11 + 0.732143 − 1.531746 7 = 10.200397 7 ≈ 1.457199
Compute
x
2
(
2
)
x
2
(
2
)
x_(2)^((2)) x_2^{(2)} x 2 ( 2 ) :
x
2
(
2
)
=
9
−
2
x
1
(
2
)
+
x
3
(
1
)
8
=
9
−
2
⋅
1.457199
+
0.765873
8
=
9
−
2.914398
+
0.765873
8
=
6.851475
8
≈
0.856434
x
2
(
2
)
=
9
−
2
x
1
(
2
)
+
x
3
(
1
)
8
=
9
−
2
⋅
1.457199
+
0.765873
8
=
9
−
2.914398
+
0.765873
8
=
6.851475
8
≈
0.856434
x_(2)^((2))=(9-2x_(1)^((2))+x_(3)^((1)))/(8)=(9-2*1.457199+0.765873)/(8)=(9-2.914398+0.765873)/(8)=(6.851475)/(8)~~0.856434 x_2^{(2)} = \frac{9 – 2x_1^{(2)} + x_3^{(1)}}{8} = \frac{9 – 2 \cdot 1.457199 + 0.765873}{8} = \frac{9 – 2.914398 + 0.765873}{8} = \frac{6.851475}{8} \approx 0.856434 x 2 ( 2 ) = 9 − 2 x 1 ( 2 ) + x 3 ( 1 ) 8 = 9 − 2 ⋅ 1.457199 + 0.765873 8 = 9 − 2.914398 + 0.765873 8 = 6.851475 8 ≈ 0.856434
Compute
x
3
(
2
)
x
3
(
2
)
x_(3)^((2)) x_3^{(2)} x 3 ( 2 ) :
x
3
(
2
)
=
7
−
x
1
(
2
)
+
2
x
2
(
2
)
9
=
7
−
1.457199
+
2
⋅
0.856434
9
=
7
−
1.457199
+
1.712868
9
=
7.255669
9
≈
0.806185
x
3
(
2
)
=
7
−
x
1
(
2
)
+
2
x
2
(
2
)
9
=
7
−
1.457199
+
2
⋅
0.856434
9
=
7
−
1.457199
+
1.712868
9
=
7.255669
9
≈
0.806185
x_(3)^((2))=(7-x_(1)^((2))+2x_(2)^((2)))/(9)=(7-1.457199+2*0.856434)/(9)=(7-1.457199+1.712868)/(9)=(7.255669)/(9)~~0.806185 x_3^{(2)} = \frac{7 – x_1^{(2)} + 2x_2^{(2)}}{9} = \frac{7 – 1.457199 + 2 \cdot 0.856434}{9} = \frac{7 – 1.457199 + 1.712868}{9} = \frac{7.255669}{9} \approx 0.806185 x 3 ( 2 ) = 7 − x 1 ( 2 ) + 2 x 2 ( 2 ) 9 = 7 − 1.457199 + 2 ⋅ 0.856434 9 = 7 − 1.457199 + 1.712868 9 = 7.255669 9 ≈ 0.806185
Results after Iteration 2:
x
1
(
2
)
≈
1.457199
,
x
2
(
2
)
≈
0.856434
,
x
3
(
2
)
≈
0.806185
x
1
(
2
)
≈
1.457199
,
x
2
(
2
)
≈
0.856434
,
x
3
(
2
)
≈
0.806185
x_(1)^((2))~~1.457199,quadx_(2)^((2))~~0.856434,quadx_(3)^((2))~~0.806185 x_1^{(2)} \approx 1.457199, \quad x_2^{(2)} \approx 0.856434, \quad x_3^{(2)} \approx 0.806185 x 1 ( 2 ) ≈ 1.457199 , x 2 ( 2 ) ≈ 0.856434 , x 3 ( 2 ) ≈ 0.806185
Check Convergence:
Calculate absolute differences:
|
x
1
(
2
)
−
x
1
(
1
)
|
=
|
1.457199
−
1.571429
|
≈
0.114230
|
x
1
(
2
)
−
x
1
(
1
)
|
=
|
1.457199
−
1.571429
|
≈
0.114230
|x_(1)^((2))-x_(1)^((1))|=|1.457199-1.571429|~~0.114230 |x_1^{(2)} – x_1^{(1)}| = |1.457199 – 1.571429| \approx 0.114230 | x 1 ( 2 ) − x 1 ( 1 ) | = | 1.457199 − 1.571429 | ≈ 0.114230
|
x
2
(
2
)
−
x
2
(
1
)
|
=
|
0.856434
−
0.732143
|
≈
0.124291
|
x
2
(
2
)
−
x
2
(
1
)
|
=
|
0.856434
−
0.732143
|
≈
0.124291
|x_(2)^((2))-x_(2)^((1))|=|0.856434-0.732143|~~0.124291 |x_2^{(2)} – x_2^{(1)}| = |0.856434 – 0.732143| \approx 0.124291 | x 2 ( 2 ) − x 2 ( 1 ) | = | 0.856434 − 0.732143 | ≈ 0.124291
|
x
3
(
2
)
−
x
3
(
1
)
|
=
|
0.806185
−
0.765873
|
≈
0.040312
|
x
3
(
2
)
−
x
3
(
1
)
|
=
|
0.806185
−
0.765873
|
≈
0.040312
|x_(3)^((2))-x_(3)^((1))|=|0.806185-0.765873|~~0.040312 |x_3^{(2)} – x_3^{(1)}| = |0.806185 – 0.765873| \approx 0.040312 | x 3 ( 2 ) − x 3 ( 1 ) | = | 0.806185 − 0.765873 | ≈ 0.040312
Since differences are greater than
0.00005
0.00005
0.00005 0.00005 0.00005 , continue iterating.
Iteration 3:
Compute
x
1
(
3
)
x
1
(
3
)
x_(1)^((3)) x_1^{(3)} x 1 ( 3 ) :
x
1
(
3
)
=
11
+
x
2
(
2
)
−
2
x
3
(
2
)
7
=
11
+
0.856434
−
2
⋅
0.806185
7
=
11
+
0.856434
−
1.612370
7
=
10.244064
7
≈
1.463438
x
1
(
3
)
=
11
+
x
2
(
2
)
−
2
x
3
(
2
)
7
=
11
+
0.856434
−
2
⋅
0.806185
7
=
11
+
0.856434
−
1.612370
7
=
10.244064
7
≈
1.463438
x_(1)^((3))=(11+x_(2)^((2))-2x_(3)^((2)))/(7)=(11+0.856434-2*0.806185)/(7)=(11+0.856434-1.612370)/(7)=(10.244064)/(7)~~1.463438 x_1^{(3)} = \frac{11 + x_2^{(2)} – 2x_3^{(2)}}{7} = \frac{11 + 0.856434 – 2 \cdot 0.806185}{7} = \frac{11 + 0.856434 – 1.612370}{7} = \frac{10.244064}{7} \approx 1.463438 x 1 ( 3 ) = 11 + x 2 ( 2 ) − 2 x 3 ( 2 ) 7 = 11 + 0.856434 − 2 ⋅ 0.806185 7 = 11 + 0.856434 − 1.612370 7 = 10.244064 7 ≈ 1.463438
Compute
x
2
(
3
)
x
2
(
3
)
x_(2)^((3)) x_2^{(3)} x 2 ( 3 ) :
x
2
(
3
)
=
9
−
2
x
1
(
3
)
+
x
3
(
2
)
8
=
9
−
2
⋅
1.463438
+
0.806185
8
=
9
−
2.926876
+
0.806185
8
=
6.879309
8
≈
0.859914
x
2
(
3
)
=
9
−
2
x
1
(
3
)
+
x
3
(
2
)
8
=
9
−
2
⋅
1.463438
+
0.806185
8
=
9
−
2.926876
+
0.806185
8
=
6.879309
8
≈
0.859914
x_(2)^((3))=(9-2x_(1)^((3))+x_(3)^((2)))/(8)=(9-2*1.463438+0.806185)/(8)=(9-2.926876+0.806185)/(8)=(6.879309)/(8)~~0.859914 x_2^{(3)} = \frac{9 – 2x_1^{(3)} + x_3^{(2)}}{8} = \frac{9 – 2 \cdot 1.463438 + 0.806185}{8} = \frac{9 – 2.926876 + 0.806185}{8} = \frac{6.879309}{8} \approx 0.859914 x 2 ( 3 ) = 9 − 2 x 1 ( 3 ) + x 3 ( 2 ) 8 = 9 − 2 ⋅ 1.463438 + 0.806185 8 = 9 − 2.926876 + 0.806185 8 = 6.879309 8 ≈ 0.859914
Compute
x
3
(
3
)
x
3
(
3
)
x_(3)^((3)) x_3^{(3)} x 3 ( 3 ) :
x
3
(
3
)
=
7
−
x
1
(
3
)
+
2
x
2
(
3
)
9
=
7
−
1.463438
+
2
⋅
0.859914
9
=
7
−
1.463438
+
1.719828
9
=
7.256390
9
≈
0.806266
x
3
(
3
)
=
7
−
x
1
(
3
)
+
2
x
2
(
3
)
9
=
7
−
1.463438
+
2
⋅
0.859914
9
=
7
−
1.463438
+
1.719828
9
=
7.256390
9
≈
0.806266
x_(3)^((3))=(7-x_(1)^((3))+2x_(2)^((3)))/(9)=(7-1.463438+2*0.859914)/(9)=(7-1.463438+1.719828)/(9)=(7.256390)/(9)~~0.806266 x_3^{(3)} = \frac{7 – x_1^{(3)} + 2x_2^{(3)}}{9} = \frac{7 – 1.463438 + 2 \cdot 0.859914}{9} = \frac{7 – 1.463438 + 1.719828}{9} = \frac{7.256390}{9} \approx 0.806266 x 3 ( 3 ) = 7 − x 1 ( 3 ) + 2 x 2 ( 3 ) 9 = 7 − 1.463438 + 2 ⋅ 0.859914 9 = 7 − 1.463438 + 1.719828 9 = 7.256390 9 ≈ 0.806266
Results after Iteration 3:
x
1
(
3
)
≈
1.463438
,
x
2
(
3
)
≈
0.859914
,
x
3
(
3
)
≈
0.806266
x
1
(
3
)
≈
1.463438
,
x
2
(
3
)
≈
0.859914
,
x
3
(
3
)
≈
0.806266
x_(1)^((3))~~1.463438,quadx_(2)^((3))~~0.859914,quadx_(3)^((3))~~0.806266 x_1^{(3)} \approx 1.463438, \quad x_2^{(3)} \approx 0.859914, \quad x_3^{(3)} \approx 0.806266 x 1 ( 3 ) ≈ 1.463438 , x 2 ( 3 ) ≈ 0.859914 , x 3 ( 3 ) ≈ 0.806266
Check Convergence:
|
x
1
(
3
)
−
x
1
(
2
)
|
=
|
1.463438
−
1.457199
|
≈
0.006239
|
x
1
(
3
)
−
x
1
(
2
)
|
=
|
1.463438
−
1.457199
|
≈
0.006239
|x_(1)^((3))-x_(1)^((2))|=|1.463438-1.457199|~~0.006239 |x_1^{(3)} – x_1^{(2)}| = |1.463438 – 1.457199| \approx 0.006239 | x 1 ( 3 ) − x 1 ( 2 ) | = | 1.463438 − 1.457199 | ≈ 0.006239
|
x
2
(
3
)
−
x
2
(
2
)
|
=
|
0.859914
−
0.856434
|
≈
0.003480
|
x
2
(
3
)
−
x
2
(
2
)
|
=
|
0.859914
−
0.856434
|
≈
0.003480
|x_(2)^((3))-x_(2)^((2))|=|0.859914-0.856434|~~0.003480 |x_2^{(3)} – x_2^{(2)}| = |0.859914 – 0.856434| \approx 0.003480 | x 2 ( 3 ) − x 2 ( 2 ) | = | 0.859914 − 0.856434 | ≈ 0.003480
|
x
3
(
3
)
−
x
3
(
2
)
|
=
|
0.806266
−
0.806185
|
≈
0.000081
|
x
3
(
3
)
−
x
3
(
2
)
|
=
|
0.806266
−
0.806185
|
≈
0.000081
|x_(3)^((3))-x_(3)^((2))|=|0.806266-0.806185|~~0.000081 |x_3^{(3)} – x_3^{(2)}| = |0.806266 – 0.806185| \approx 0.000081 | x 3 ( 3 ) − x 3 ( 2 ) | = | 0.806266 − 0.806185 | ≈ 0.000081
Since
|
x
3
(
3
)
−
x
3
(
2
)
|
≈
0.000081
>
0.00005
|
x
3
(
3
)
−
x
3
(
2
)
|
≈
0.000081
>
0.00005
|x_(3)^((3))-x_(3)^((2))|~~0.000081 > 0.00005 |x_3^{(3)} – x_3^{(2)}| \approx 0.000081 > 0.00005 | x 3 ( 3 ) − x 3 ( 2 ) | ≈ 0.000081 > 0.00005 , continue.
Iteration 4:
Compute
x
1
(
4
)
x
1
(
4
)
x_(1)^((4)) x_1^{(4)} x 1 ( 4 ) :
x
1
(
4
)
=
11
+
x
2
(
3
)
−
2
x
3
(
3
)
7
=
11
+
0.859914
−
2
⋅
0.806266
7
=
11
+
0.859914
−
1.612532
7
=
10.247382
7
≈
1.463912
x
1
(
4
)
=
11
+
x
2
(
3
)
−
2
x
3
(
3
)
7
=
11
+
0.859914
−
2
⋅
0.806266
7
=
11
+
0.859914
−
1.612532
7
=
10.247382
7
≈
1.463912
x_(1)^((4))=(11+x_(2)^((3))-2x_(3)^((3)))/(7)=(11+0.859914-2*0.806266)/(7)=(11+0.859914-1.612532)/(7)=(10.247382)/(7)~~1.463912 x_1^{(4)} = \frac{11 + x_2^{(3)} – 2x_3^{(3)}}{7} = \frac{11 + 0.859914 – 2 \cdot 0.806266}{7} = \frac{11 + 0.859914 – 1.612532}{7} = \frac{10.247382}{7} \approx 1.463912 x 1 ( 4 ) = 11 + x 2 ( 3 ) − 2 x 3 ( 3 ) 7 = 11 + 0.859914 − 2 ⋅ 0.806266 7 = 11 + 0.859914 − 1.612532 7 = 10.247382 7 ≈ 1.463912
Compute
x
2
(
4
)
x
2
(
4
)
x_(2)^((4)) x_2^{(4)} x 2 ( 4 ) :
x
2
(
4
)
=
9
−
2
x
1
(
4
)
+
x
3
(
3
)
8
=
9
−
2
⋅
1.463912
+
0.806266
8
=
9
−
2.927824
+
0.806266
8
=
6.878442
8
≈
0.859805
x
2
(
4
)
=
9
−
2
x
1
(
4
)
+
x
3
(
3
)
8
=
9
−
2
⋅
1.463912
+
0.806266
8
=
9
−
2.927824
+
0.806266
8
=
6.878442
8
≈
0.859805
x_(2)^((4))=(9-2x_(1)^((4))+x_(3)^((3)))/(8)=(9-2*1.463912+0.806266)/(8)=(9-2.927824+0.806266)/(8)=(6.878442)/(8)~~0.859805 x_2^{(4)} = \frac{9 – 2x_1^{(4)} + x_3^{(3)}}{8} = \frac{9 – 2 \cdot 1.463912 + 0.806266}{8} = \frac{9 – 2.927824 + 0.806266}{8} = \frac{6.878442}{8} \approx 0.859805 x 2 ( 4 ) = 9 − 2 x 1 ( 4 ) + x 3 ( 3 ) 8 = 9 − 2 ⋅ 1.463912 + 0.806266 8 = 9 − 2.927824 + 0.806266 8 = 6.878442 8 ≈ 0.859805
Compute
x
3
(
4
)
x
3
(
4
)
x_(3)^((4)) x_3^{(4)} x 3 ( 4 ) :
x
3
(
4
)
=
7
−
x
1
(
4
)
+
2
x
2
(
4
)
9
=
7
−
1.463912
+
2
⋅
0.859805
9
=
7
−
1.463912
+
1.719610
9
=
7.255698
9
≈
0.806189
x
3
(
4
)
=
7
−
x
1
(
4
)
+
2
x
2
(
4
)
9
=
7
−
1.463912
+
2
⋅
0.859805
9
=
7
−
1.463912
+
1.719610
9
=
7.255698
9
≈
0.806189
x_(3)^((4))=(7-x_(1)^((4))+2x_(2)^((4)))/(9)=(7-1.463912+2*0.859805)/(9)=(7-1.463912+1.719610)/(9)=(7.255698)/(9)~~0.806189 x_3^{(4)} = \frac{7 – x_1^{(4)} + 2x_2^{(4)}}{9} = \frac{7 – 1.463912 + 2 \cdot 0.859805}{9} = \frac{7 – 1.463912 + 1.719610}{9} = \frac{7.255698}{9} \approx 0.806189 x 3 ( 4 ) = 7 − x 1 ( 4 ) + 2 x 2 ( 4 ) 9 = 7 − 1.463912 + 2 ⋅ 0.859805 9 = 7 − 1.463912 + 1.719610 9 = 7.255698 9 ≈ 0.806189
Results after Iteration 4:
x
1
(
4
)
≈
1.463912
,
x
2
(
4
)
≈
0.859805
,
x
3
(
4
)
≈
0.806189
x
1
(
4
)
≈
1.463912
,
x
2
(
4
)
≈
0.859805
,
x
3
(
4
)
≈
0.806189
x_(1)^((4))~~1.463912,quadx_(2)^((4))~~0.859805,quadx_(3)^((4))~~0.806189 x_1^{(4)} \approx 1.463912, \quad x_2^{(4)} \approx 0.859805, \quad x_3^{(4)} \approx 0.806189 x 1 ( 4 ) ≈ 1.463912 , x 2 ( 4 ) ≈ 0.859805 , x 3 ( 4 ) ≈ 0.806189
Check Convergence:
|
x
1
(
4
)
−
x
1
(
3
)
|
=
|
1.463912
−
1.463438
|
≈
0.000474
|
x
1
(
4
)
−
x
1
(
3
)
|
=
|
1.463912
−
1.463438
|
≈
0.000474
|x_(1)^((4))-x_(1)^((3))|=|1.463912-1.463438|~~0.000474 |x_1^{(4)} – x_1^{(3)}| = |1.463912 – 1.463438| \approx 0.000474 | x 1 ( 4 ) − x 1 ( 3 ) | = | 1.463912 − 1.463438 | ≈ 0.000474
|
x
2
(
4
)
−
x
2
(
3
)
|
=
|
0.859805
−
0.859914
|
≈
0.000109
|
x
2
(
4
)
−
x
2
(
3
)
|
=
|
0.859805
−
0.859914
|
≈
0.000109
|x_(2)^((4))-x_(2)^((3))|=|0.859805-0.859914|~~0.000109 |x_2^{(4)} – x_2^{(3)}| = |0.859805 – 0.859914| \approx 0.000109 | x 2 ( 4 ) − x 2 ( 3 ) | = | 0.859805 − 0.859914 | ≈ 0.000109
|
x
3
(
4
)
−
x
3
(
3
)
|
=
|
0.806189
−
0.806266
|
≈
0.000077
|
x
3
(
4
)
−
x
3
(
3
)
|
=
|
0.806189
−
0.806266
|
≈
0.000077
|x_(3)^((4))-x_(3)^((3))|=|0.806189-0.806266|~~0.000077 |x_3^{(4)} – x_3^{(3)}| = |0.806189 – 0.806266| \approx 0.000077 | x 3 ( 4 ) − x 3 ( 3 ) | = | 0.806189 − 0.806266 | ≈ 0.000077
Since differences are still above
0.00005
0.00005
0.00005 0.00005 0.00005 , continue.
Iteration 5:
Compute
x
1
(
5
)
x
1
(
5
)
x_(1)^((5)) x_1^{(5)} x 1 ( 5 ) :
x
1
(
5
)
=
11
+
x
2
(
4
)
−
2
x
3
(
4
)
7
=
11
+
0.859805
−
2
⋅
0.806189
7
=
11
+
0.859805
−
1.612378
7
=
10.247427
7
≈
1.463918
x
1
(
5
)
=
11
+
x
2
(
4
)
−
2
x
3
(
4
)
7
=
11
+
0.859805
−
2
⋅
0.806189
7
=
11
+
0.859805
−
1.612378
7
=
10.247427
7
≈
1.463918
x_(1)^((5))=(11+x_(2)^((4))-2x_(3)^((4)))/(7)=(11+0.859805-2*0.806189)/(7)=(11+0.859805-1.612378)/(7)=(10.247427)/(7)~~1.463918 x_1^{(5)} = \frac{11 + x_2^{(4)} – 2x_3^{(4)}}{7} = \frac{11 + 0.859805 – 2 \cdot 0.806189}{7} = \frac{11 + 0.859805 – 1.612378}{7} = \frac{10.247427}{7} \approx 1.463918 x 1 ( 5 ) = 11 + x 2 ( 4 ) − 2 x 3 ( 4 ) 7 = 11 + 0.859805 − 2 ⋅ 0.806189 7 = 11 + 0.859805 − 1.612378 7 = 10.247427 7 ≈ 1.463918
Compute
x
2
(
5
)
x
2
(
5
)
x_(2)^((5)) x_2^{(5)} x 2 ( 5 ) :
x
2
(
5
)
=
9
−
2
x
1
(
5
)
+
x
3
(
4
)
8
=
9
−
2
⋅
1.463918
+
0.806189
8
=
9
−
2.927836
+
0.806189
8
=
6.878353
8
≈
0.859794
x
2
(
5
)
=
9
−
2
x
1
(
5
)
+
x
3
(
4
)
8
=
9
−
2
⋅
1.463918
+
0.806189
8
=
9
−
2.927836
+
0.806189
8
=
6.878353
8
≈
0.859794
x_(2)^((5))=(9-2x_(1)^((5))+x_(3)^((4)))/(8)=(9-2*1.463918+0.806189)/(8)=(9-2.927836+0.806189)/(8)=(6.878353)/(8)~~0.859794 x_2^{(5)} = \frac{9 – 2x_1^{(5)} + x_3^{(4)}}{8} = \frac{9 – 2 \cdot 1.463918 + 0.806189}{8} = \frac{9 – 2.927836 + 0.806189}{8} = \frac{6.878353}{8} \approx 0.859794 x 2 ( 5 ) = 9 − 2 x 1 ( 5 ) + x 3 ( 4 ) 8 = 9 − 2 ⋅ 1.463918 + 0.806189 8 = 9 − 2.927836 + 0.806189 8 = 6.878353 8 ≈ 0.859794
Compute
x
3
(
5
)
x
3
(
5
)
x_(3)^((5)) x_3^{(5)} x 3 ( 5 ) :
x
3
(
5
)
=
7
−
x
1
(
5
)
+
2
x
2
(
5
)
9
=
7
−
1.463918
+
2
⋅
0.859794
9
=
7
−
1.463918
+
1.719588
9
=
7.255670
9
≈
0.806186
x
3
(
5
)
=
7
−
x
1
(
5
)
+
2
x
2
(
5
)
9
=
7
−
1.463918
+
2
⋅
0.859794
9
=
7
−
1.463918
+
1.719588
9
=
7.255670
9
≈
0.806186
x_(3)^((5))=(7-x_(1)^((5))+2x_(2)^((5)))/(9)=(7-1.463918+2*0.859794)/(9)=(7-1.463918+1.719588)/(9)=(7.255670)/(9)~~0.806186 x_3^{(5)} = \frac{7 – x_1^{(5)} + 2x_2^{(5)}}{9} = \frac{7 – 1.463918 + 2 \cdot 0.859794}{9} = \frac{7 – 1.463918 + 1.719588}{9} = \frac{7.255670}{9} \approx 0.806186 x 3 ( 5 ) = 7 − x 1 ( 5 ) + 2 x 2 ( 5 ) 9 = 7 − 1.463918 + 2 ⋅ 0.859794 9 = 7 − 1.463918 + 1.719588 9 = 7.255670 9 ≈ 0.806186
Results after Iteration 5:
x
1
(
5
)
≈
1.463918
,
x
2
(
5
)
≈
0.859794
,
x
3
(
5
)
≈
0.806186
x
1
(
5
)
≈
1.463918
,
x
2
(
5
)
≈
0.859794
,
x
3
(
5
)
≈
0.806186
x_(1)^((5))~~1.463918,quadx_(2)^((5))~~0.859794,quadx_(3)^((5))~~0.806186 x_1^{(5)} \approx 1.463918, \quad x_2^{(5)} \approx 0.859794, \quad x_3^{(5)} \approx 0.806186 x 1 ( 5 ) ≈ 1.463918 , x 2 ( 5 ) ≈ 0.859794 , x 3 ( 5 ) ≈ 0.806186
Check Convergence:
|
x
1
(
5
)
−
x
1
(
4
)
|
=
|
1.463918
−
1.463912
|
≈
0.000006
|
x
1
(
5
)
−
x
1
(
4
)
|
=
|
1.463918
−
1.463912
|
≈
0.000006
|x_(1)^((5))-x_(1)^((4))|=|1.463918-1.463912|~~0.000006 |x_1^{(5)} – x_1^{(4)}| = |1.463918 – 1.463912| \approx 0.000006 | x 1 ( 5 ) − x 1 ( 4 ) | = | 1.463918 − 1.463912 | ≈ 0.000006
|
x
2
(
5
)
−
x
2
(
4
)
|
=
|
0.859794
−
0.859805
|
≈
0.000011
|
x
2
(
5
)
−
x
2
(
4
)
|
=
|
0.859794
−
0.859805
|
≈
0.000011
|x_(2)^((5))-x_(2)^((4))|=|0.859794-0.859805|~~0.000011 |x_2^{(5)} – x_2^{(4)}| = |0.859794 – 0.859805| \approx 0.000011 | x 2 ( 5 ) − x 2 ( 4 ) | = | 0.859794 − 0.859805 | ≈ 0.000011
|
x
3
(
5
)
−
x
3
(
4
)
|
=
|
0.806186
−
0.806189
|
≈
0.000003
|
x
3
(
5
)
−
x
3
(
4
)
|
=
|
0.806186
−
0.806189
|
≈
0.000003
|x_(3)^((5))-x_(3)^((4))|=|0.806186-0.806189|~~0.000003 |x_3^{(5)} – x_3^{(4)}| = |0.806186 – 0.806189| \approx 0.000003 | x 3 ( 5 ) − x 3 ( 4 ) | = | 0.806186 − 0.806189 | ≈ 0.000003
All differences are less than
0.00005
0.00005
0.00005 0.00005 0.00005 , indicating convergence to 4 significant figures.
Final Answer
To 4 significant figures:
x
1
≈
1.464
,
x
2
≈
0.8598
,
x
3
≈
0.8062
x
1
≈
1.464
,
x
2
≈
0.8598
,
x
3
≈
0.8062
x_(1)~~1.464,quadx_(2)~~0.8598,quadx_(3)~~0.8062 x_1 \approx 1.464, \quad x_2 \approx 0.8598, \quad x_3 \approx 0.8062 x 1 ≈ 1.464 , x 2 ≈ 0.8598 , x 3 ≈ 0.8062
Verification:
Substitute
x
1
=
1.464
x
1
=
1.464
x_(1)=1.464 x_1 = 1.464 x 1 = 1.464 ,
x
2
=
0.8598
x
2
=
0.8598
x_(2)=0.8598 x_2 = 0.8598 x 2 = 0.8598 ,
x
3
=
0.8062
x
3
=
0.8062
x_(3)=0.8062 x_3 = 0.8062 x 3 = 0.8062 into the original equations:
7
x
1
−
x
2
+
2
x
3
=
7
⋅
1.464
−
0.8598
+
2
⋅
0.8062
=
10.248
−
0.8598
+
1.6124
=
11.0006
≈
11
7
x
1
−
x
2
+
2
x
3
=
7
⋅
1.464
−
0.8598
+
2
⋅
0.8062
=
10.248
−
0.8598
+
1.6124
=
11.0006
≈
11
7x_(1)-x_(2)+2x_(3)=7*1.464-0.8598+2*0.8062=10.248-0.8598+1.6124=11.0006~~11 7x_1 – x_2 + 2x_3 = 7 \cdot 1.464 – 0.8598 + 2 \cdot 0.8062 = 10.248 – 0.8598 + 1.6124 = 11.0006 \approx 11 7 x 1 − x 2 + 2 x 3 = 7 ⋅ 1.464 − 0.8598 + 2 ⋅ 0.8062 = 10.248 − 0.8598 + 1.6124 = 11.0006 ≈ 11
2
x
1
+
8
x
2
−
x
3
=
2
⋅
1.464
+
8
⋅
0.8598
−
0.8062
=
2.928
+
6.8784
−
0.8062
=
9.0002
≈
9
2
x
1
+
8
x
2
−
x
3
=
2
⋅
1.464
+
8
⋅
0.8598
−
0.8062
=
2.928
+
6.8784
−
0.8062
=
9.0002
≈
9
2x_(1)+8x_(2)-x_(3)=2*1.464+8*0.8598-0.8062=2.928+6.8784-0.8062=9.0002~~9 2x_1 + 8x_2 – x_3 = 2 \cdot 1.464 + 8 \cdot 0.8598 – 0.8062 = 2.928 + 6.8784 – 0.8062 = 9.0002 \approx 9 2 x 1 + 8 x 2 − x 3 = 2 ⋅ 1.464 + 8 ⋅ 0.8598 − 0.8062 = 2.928 + 6.8784 − 0.8062 = 9.0002 ≈ 9
x
1
−
2
x
2
+
9
x
3
=
1.464
−
2
⋅
0.8598
+
9
⋅
0.8062
=
1.464
−
1.7196
+
7.2558
=
7.0002
≈
7
x
1
−
2
x
2
+
9
x
3
=
1.464
−
2
⋅
0.8598
+
9
⋅
0.8062
=
1.464
−
1.7196
+
7.2558
=
7.0002
≈
7
x_(1)-2x_(2)+9x_(3)=1.464-2*0.8598+9*0.8062=1.464-1.7196+7.2558=7.0002~~7 x_1 – 2x_2 + 9x_3 = 1.464 – 2 \cdot 0.8598 + 9 \cdot 0.8062 = 1.464 – 1.7196 + 7.2558 = 7.0002 \approx 7 x 1 − 2 x 2 + 9 x 3 = 1.464 − 2 ⋅ 0.8598 + 9 ⋅ 0.8062 = 1.464 − 1.7196 + 7.2558 = 7.0002 ≈ 7
The values satisfy the equations within a small error, confirming the solution.
Thus, the solution to the system, correct to 4 significant figures, is:
x
1
=
1.464
,
x
2
=
0.8598
,
x
3
=
0.8062
x
1
=
1.464
,
x
2
=
0.8598
,
x
3
=
0.8062
x_(1)=1.464,quadx_(2)=0.8598,quadx_(3)=0.8062 \boxed{x_1 = 1.464, \quad x_2 = 0.8598, \quad x_3 = 0.8062} x 1 = 1.464 , x 2 = 0.8598 , x 3 = 0.8062
Question:-06 (c)
A mechanical system with 2 degrees of freedom has the Lagrangian
L
=
1
2
m
(
x
˙
2
+
y
˙
2
)
−
1
2
m
(
w
1
2
x
2
+
w
2
2
y
2
)
+
k
x
y
L
=
1
2
m
(
x
˙
2
+
y
˙
2
)
−
1
2
m
(
w
1
2
x
2
+
w
2
2
y
2
)
+
k
x
y
L=(1)/(2)m(x^(˙)^(2)+y^(˙)^(2))-(1)/(2)m(w_(1)^(2)x^(2)+w_(2)^(2)y^(2))+kxy L = \frac{1}{2} m (\dot{x}^2 + \dot{y}^2) – \frac{1}{2} m (w_1^2 x^2 + w_2^2 y^2) + k x y L = 1 2 m ( x ˙ 2 + y ˙ 2 ) − 1 2 m ( w 1 2 x 2 + w 2 2 y 2 ) + k x y
where
m
,
w
1
,
w
2
,
k
m
,
w
1
,
w
2
,
k
m,w_(1),w_(2),k m, w_1, w_2, k m , w 1 , w 2 , k are constants. Find the parameter
θ
θ
theta \theta θ so that under the transformation
x
=
q
1
cos
θ
−
q
2
sin
θ
,
y
=
q
1
sin
θ
+
q
2
cos
θ
x
=
q
1
cos
θ
−
q
2
sin
θ
,
y
=
q
1
sin
θ
+
q
2
cos
θ
x=q_(1)cos theta-q_(2)sin theta,quad y=q_(1)sin theta+q_(2)cos theta x = q_1 \cos \theta – q_2 \sin \theta, \quad y = q_1 \sin \theta + q_2 \cos \theta x = q 1 cos θ − q 2 sin θ , y = q 1 sin θ + q 2 cos θ
the Lagrangian in terms of
q
1
,
q
2
q
1
,
q
2
q_(1),q_(2) q_1, q_2 q 1 , q 2 will not contain the product term
q
1
q
2
q
1
q
2
q_(1)q_(2) q_1 q_2 q 1 q 2 . Find the Lagrange’s equations with respect to
q
1
q
1
q_(1) q_1 q 1 and
q
2
q
2
q_(2) q_2 q 2 independent of parameter
θ
θ
theta \theta θ .
Answer:
To eliminate the cross term
q
1
q
2
q
1
q
2
q_(1)q_(2) q_1 q_2 q 1 q 2 in the Lagrangian, we perform a coordinate transformation and determine the angle
θ
θ
theta \theta θ that decouples the system. Here’s the step-by-step solution:
Given Lagrangian:
L
=
1
2
m
(
x
˙
2
+
y
˙
2
)
−
1
2
m
(
w
1
2
x
2
+
w
2
2
y
2
)
+
k
x
y
L
=
1
2
m
(
x
˙
2
+
y
˙
2
)
−
1
2
m
(
w
1
2
x
2
+
w
2
2
y
2
)
+
k
x
y
L=(1)/(2)m(x^(˙)^(2)+y^(˙)^(2))-(1)/(2)m(w_(1)^(2)x^(2)+w_(2)^(2)y^(2))+kxy L = \frac{1}{2} m (\dot{x}^2 + \dot{y}^2) – \frac{1}{2} m (w_1^2 x^2 + w_2^2 y^2) + k x y L = 1 2 m ( x ˙ 2 + y ˙ 2 ) − 1 2 m ( w 1 2 x 2 + w 2 2 y 2 ) + k x y
x
=
q
1
cos
θ
−
q
2
sin
θ
,
y
=
q
1
sin
θ
+
q
2
cos
θ
.
x
=
q
1
cos
θ
−
q
2
sin
θ
,
y
=
q
1
sin
θ
+
q
2
cos
θ
.
{:[x=q_(1)cos theta-q_(2)sin theta”,”],[y=q_(1)sin theta+q_(2)cos theta.]:} \begin{aligned}
x &= q_1 \cos \theta – q_2 \sin \theta, \\
y &= q_1 \sin \theta + q_2 \cos \theta.
\end{aligned} x = q 1 cos θ − q 2 sin θ , y = q 1 sin θ + q 2 cos θ .
Step 1: Express
x
˙
2
+
y
˙
2
x
˙
2
+
y
˙
2
x^(˙)^(2)+y^(˙)^(2) \dot{x}^2 + \dot{y}^2 x ˙ 2 + y ˙ 2 in terms of
q
˙
1
,
q
˙
2
q
˙
1
,
q
˙
2
q^(˙)_(1),q^(˙)_(2) \dot{q}_1, \dot{q}_2 q ˙ 1 , q ˙ 2 :
Differentiating
x
x
x x x and
y
y
y y y :
x
˙
=
q
˙
1
cos
θ
−
q
˙
2
sin
θ
,
y
˙
=
q
˙
1
sin
θ
+
q
˙
2
cos
θ
.
x
˙
=
q
˙
1
cos
θ
−
q
˙
2
sin
θ
,
y
˙
=
q
˙
1
sin
θ
+
q
˙
2
cos
θ
.
{:[x^(˙)=q^(˙)_(1)cos theta-q^(˙)_(2)sin theta”,”],[y^(˙)=q^(˙)_(1)sin theta+q^(˙)_(2)cos theta.]:} \begin{aligned}
\dot{x} &= \dot{q}_1 \cos \theta – \dot{q}_2 \sin \theta, \\
\dot{y} &= \dot{q}_1 \sin \theta + \dot{q}_2 \cos \theta.
\end{aligned} x ˙ = q ˙ 1 cos θ − q ˙ 2 sin θ , y ˙ = q ˙ 1 sin θ + q ˙ 2 cos θ .
Thus,
x
˙
2
+
y
˙
2
=
q
˙
1
2
+
q
˙
2
2
.
x
˙
2
+
y
˙
2
=
q
˙
1
2
+
q
˙
2
2
.
x^(˙)^(2)+y^(˙)^(2)=q^(˙)_(1)^(2)+q^(˙)_(2)^(2). \dot{x}^2 + \dot{y}^2 = \dot{q}_1^2 + \dot{q}_2^2. x ˙ 2 + y ˙ 2 = q ˙ 1 2 + q ˙ 2 2 .
Step 2: Express the potential terms in terms of
q
1
,
q
2
q
1
,
q
2
q_(1),q_(2) q_1, q_2 q 1 , q 2 :
Substitute
x
x
x x x and
y
y
y y y into the potential terms:
w
1
2
x
2
+
w
2
2
y
2
=
w
1
2
(
q
1
cos
θ
−
q
2
sin
θ
)
2
+
w
2
2
(
q
1
sin
θ
+
q
2
cos
θ
)
2
=
w
1
2
(
q
1
2
cos
2
θ
−
2
q
1
q
2
cos
θ
sin
θ
+
q
2
2
sin
2
θ
)
+
w
2
2
(
q
1
2
sin
2
θ
+
2
q
1
q
2
sin
θ
cos
θ
+
q
2
2
cos
2
θ
)
=
q
1
2
(
w
1
2
cos
2
θ
+
w
2
2
sin
2
θ
)
+
q
2
2
(
w
1
2
sin
2
θ
+
w
2
2
cos
2
θ
)
+
2
q
1
q
2
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
.
w
1
2
x
2
+
w
2
2
y
2
=
w
1
2
(
q
1
cos
θ
−
q
2
sin
θ
)
2
+
w
2
2
(
q
1
sin
θ
+
q
2
cos
θ
)
2
=
w
1
2
(
q
1
2
cos
2
θ
−
2
q
1
q
2
cos
θ
sin
θ
+
q
2
2
sin
2
θ
)
+
w
2
2
(
q
1
2
sin
2
θ
+
2
q
1
q
2
sin
θ
cos
θ
+
q
2
2
cos
2
θ
)
=
q
1
2
(
w
1
2
cos
2
θ
+
w
2
2
sin
2
θ
)
+
q
2
2
(
w
1
2
sin
2
θ
+
w
2
2
cos
2
θ
)
+
2
q
1
q
2
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
.
{:[w_(1)^(2)x^(2)+w_(2)^(2)y^(2)=w_(1)^(2)(q_(1)cos theta-q_(2)sin theta)^(2)+w_(2)^(2)(q_(1)sin theta+q_(2)cos theta)^(2)],[=w_(1)^(2)(q_(1)^(2)cos^(2)theta-2q_(1)q_(2)cos theta sin theta+q_(2)^(2)sin^(2)theta)],[quad+w_(2)^(2)(q_(1)^(2)sin^(2)theta+2q_(1)q_(2)sin theta cos theta+q_(2)^(2)cos^(2)theta)],[=q_(1)^(2)(w_(1)^(2)cos^(2)theta+w_(2)^(2)sin^(2)theta)+q_(2)^(2)(w_(1)^(2)sin^(2)theta+w_(2)^(2)cos^(2)theta)],[quad+2q_(1)q_(2)(w_(2)^(2)-w_(1)^(2))sin theta cos theta.]:} \begin{aligned}
w_1^2 x^2 + w_2^2 y^2 &= w_1^2 (q_1 \cos \theta – q_2 \sin \theta)^2 + w_2^2 (q_1 \sin \theta + q_2 \cos \theta)^2 \\
&= w_1^2 (q_1^2 \cos^2 \theta – 2 q_1 q_2 \cos \theta \sin \theta + q_2^2 \sin^2 \theta) \\
&\quad + w_2^2 (q_1^2 \sin^2 \theta + 2 q_1 q_2 \sin \theta \cos \theta + q_2^2 \cos^2 \theta) \\
&= q_1^2 (w_1^2 \cos^2 \theta + w_2^2 \sin^2 \theta) + q_2^2 (w_1^2 \sin^2 \theta + w_2^2 \cos^2 \theta) \\
&\quad + 2 q_1 q_2 (w_2^2 – w_1^2) \sin \theta \cos \theta.
\end{aligned} w 1 2 x 2 + w 2 2 y 2 = w 1 2 ( q 1 cos θ − q 2 sin θ ) 2 + w 2 2 ( q 1 sin θ + q 2 cos θ ) 2 = w 1 2 ( q 1 2 cos 2 θ − 2 q 1 q 2 cos θ sin θ + q 2 2 sin 2 θ ) + w 2 2 ( q 1 2 sin 2 θ + 2 q 1 q 2 sin θ cos θ + q 2 2 cos 2 θ ) = q 1 2 ( w 1 2 cos 2 θ + w 2 2 sin 2 θ ) + q 2 2 ( w 1 2 sin 2 θ + w 2 2 cos 2 θ ) + 2 q 1 q 2 ( w 2 2 − w 1 2 ) sin θ cos θ .
Similarly, the cross term
k
x
y
k
x
y
kxy k x y k x y becomes:
k
x
y
=
k
(
q
1
cos
θ
−
q
2
sin
θ
)
(
q
1
sin
θ
+
q
2
cos
θ
)
=
k
(
q
1
2
sin
θ
cos
θ
+
q
1
q
2
cos
2
θ
−
q
1
q
2
sin
2
θ
−
q
2
2
sin
θ
cos
θ
)
=
k
[
1
2
q
1
2
sin
2
θ
+
q
1
q
2
(
cos
2
θ
−
sin
2
θ
)
−
1
2
q
2
2
sin
2
θ
]
=
k
[
1
2
(
q
1
2
−
q
2
2
)
sin
2
θ
+
q
1
q
2
cos
2
θ
]
.
k
x
y
=
k
(
q
1
cos
θ
−
q
2
sin
θ
)
(
q
1
sin
θ
+
q
2
cos
θ
)
=
k
(
q
1
2
sin
θ
cos
θ
+
q
1
q
2
cos
2
θ
−
q
1
q
2
sin
2
θ
−
q
2
2
sin
θ
cos
θ
)
=
k
1
2
q
1
2
sin
2
θ
+
q
1
q
2
(
cos
2
θ
−
sin
2
θ
)
−
1
2
q
2
2
sin
2
θ
=
k
1
2
(
q
1
2
−
q
2
2
)
sin
2
θ
+
q
1
q
2
cos
2
θ
.
{:[kxy=k(q_(1)cos theta-q_(2)sin theta)(q_(1)sin theta+q_(2)cos theta)],[=k(q_(1)^(2)sin theta cos theta+q_(1)q_(2)cos^(2)theta-q_(1)q_(2)sin^(2)theta-q_(2)^(2)sin theta cos theta)],[=k[(1)/(2)q_(1)^(2)sin 2theta+q_(1)q_(2)(cos^(2)theta-sin^(2)theta)-(1)/(2)q_(2)^(2)sin 2theta]],[=k[(1)/(2)(q_(1)^(2)-q_(2)^(2))sin 2theta+q_(1)q_(2)cos 2theta].]:} \begin{aligned}
k x y &= k (q_1 \cos \theta – q_2 \sin \theta)(q_1 \sin \theta + q_2 \cos \theta) \\
&= k (q_1^2 \sin \theta \cos \theta + q_1 q_2 \cos^2 \theta – q_1 q_2 \sin^2 \theta – q_2^2 \sin \theta \cos \theta) \\
&= k \left[ \frac{1}{2} q_1^2 \sin 2\theta + q_1 q_2 (\cos^2 \theta – \sin^2 \theta) – \frac{1}{2} q_2^2 \sin 2\theta \right] \\
&= k \left[ \frac{1}{2} (q_1^2 – q_2^2) \sin 2\theta + q_1 q_2 \cos 2\theta \right].
\end{aligned} k x y = k ( q 1 cos θ − q 2 sin θ ) ( q 1 sin θ + q 2 cos θ ) = k ( q 1 2 sin θ cos θ + q 1 q 2 cos 2 θ − q 1 q 2 sin 2 θ − q 2 2 sin θ cos θ ) = k [ 1 2 q 1 2 sin 2 θ + q 1 q 2 ( cos 2 θ − sin 2 θ ) − 1 2 q 2 2 sin 2 θ ] = k [ 1 2 ( q 1 2 − q 2 2 ) sin 2 θ + q 1 q 2 cos 2 θ ] .
Step 3: Combine all terms in the Lagrangian:
The Lagrangian in terms of
q
1
,
q
2
q
1
,
q
2
q_(1),q_(2) q_1, q_2 q 1 , q 2 is:
L
=
1
2
m
(
q
˙
1
2
+
q
˙
2
2
)
−
1
2
m
[
q
1
2
(
w
1
2
cos
2
θ
+
w
2
2
sin
2
θ
)
+
q
2
2
(
w
1
2
sin
2
θ
+
w
2
2
cos
2
θ
)
]
−
1
2
m
[
2
q
1
q
2
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
]
+
k
[
1
2
(
q
1
2
−
q
2
2
)
sin
2
θ
+
q
1
q
2
cos
2
θ
]
.
L
=
1
2
m
(
q
˙
1
2
+
q
˙
2
2
)
−
1
2
m
q
1
2
(
w
1
2
cos
2
θ
+
w
2
2
sin
2
θ
)
+
q
2
2
(
w
1
2
sin
2
θ
+
w
2
2
cos
2
θ
)
−
1
2
m
2
q
1
q
2
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
+
k
1
2
(
q
1
2
−
q
2
2
)
sin
2
θ
+
q
1
q
2
cos
2
θ
.
{:[L=(1)/(2)m(q^(˙)_(1)^(2)+q^(˙)_(2)^(2))-(1)/(2)m[q_(1)^(2)(w_(1)^(2)cos^(2)theta+w_(2)^(2)sin^(2)theta)+q_(2)^(2)(w_(1)^(2)sin^(2)theta+w_(2)^(2)cos^(2)theta)]],[quad-(1)/(2)m[2q_(1)q_(2)(w_(2)^(2)-w_(1)^(2))sin theta cos theta]+k[(1)/(2)(q_(1)^(2)-q_(2)^(2))sin 2theta+q_(1)q_(2)cos 2theta].]:} \begin{aligned}
L &= \frac{1}{2} m (\dot{q}_1^2 + \dot{q}_2^2) – \frac{1}{2} m \left[ q_1^2 (w_1^2 \cos^2 \theta + w_2^2 \sin^2 \theta) + q_2^2 (w_1^2 \sin^2 \theta + w_2^2 \cos^2 \theta) \right] \\
&\quad – \frac{1}{2} m \left[ 2 q_1 q_2 (w_2^2 – w_1^2) \sin \theta \cos \theta \right] + k \left[ \frac{1}{2} (q_1^2 – q_2^2) \sin 2\theta + q_1 q_2 \cos 2\theta \right].
\end{aligned} L = 1 2 m ( q ˙ 1 2 + q ˙ 2 2 ) − 1 2 m [ q 1 2 ( w 1 2 cos 2 θ + w 2 2 sin 2 θ ) + q 2 2 ( w 1 2 sin 2 θ + w 2 2 cos 2 θ ) ] − 1 2 m [ 2 q 1 q 2 ( w 2 2 − w 1 2 ) sin θ cos θ ] + k [ 1 2 ( q 1 2 − q 2 2 ) sin 2 θ + q 1 q 2 cos 2 θ ] .
Step 4: Eliminate the
q
1
q
2
q
1
q
2
q_(1)q_(2) q_1 q_2 q 1 q 2 term:
The coefficient of
q
1
q
2
q
1
q
2
q_(1)q_(2) q_1 q_2 q 1 q 2 must be zero for the Lagrangian to be decoupled:
−
m
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
+
k
cos
2
θ
=
0.
−
m
(
w
2
2
−
w
1
2
)
sin
θ
cos
θ
+
k
cos
2
θ
=
0.
-m(w_(2)^(2)-w_(1)^(2))sin theta cos theta+k cos 2theta=0. – m (w_2^2 – w_1^2) \sin \theta \cos \theta + k \cos 2\theta = 0. − m ( w 2 2 − w 1 2 ) sin θ cos θ + k cos 2 θ = 0.
Using
sin
θ
cos
θ
=
1
2
sin
2
θ
sin
θ
cos
θ
=
1
2
sin
2
θ
sin theta cos theta=(1)/(2)sin 2theta \sin \theta \cos \theta = \frac{1}{2} \sin 2\theta sin θ cos θ = 1 2 sin 2 θ and
cos
2
θ
=
cos
2
θ
−
sin
2
θ
cos
2
θ
=
cos
2
θ
−
sin
2
θ
cos 2theta=cos^(2)theta-sin^(2)theta \cos 2\theta = \cos^2 \theta – \sin^2 \theta cos 2 θ = cos 2 θ − sin 2 θ , we get:
−
m
2
(
w
2
2
−
w
1
2
)
sin
2
θ
+
k
cos
2
θ
=
0.
−
m
2
(
w
2
2
−
w
1
2
)
sin
2
θ
+
k
cos
2
θ
=
0.
-(m)/(2)(w_(2)^(2)-w_(1)^(2))sin 2theta+k cos 2theta=0. – \frac{m}{2} (w_2^2 – w_1^2) \sin 2\theta + k \cos 2\theta = 0. − m 2 ( w 2 2 − w 1 2 ) sin 2 θ + k cos 2 θ = 0.
Rearranging:
tan
2
θ
=
2
k
m
(
w
2
2
−
w
1
2
)
.
tan
2
θ
=
2
k
m
(
w
2
2
−
w
1
2
)
.
tan 2theta=(2k)/(m(w_(2)^(2)-w_(1)^(2))). \tan 2\theta = \frac{2k}{m (w_2^2 – w_1^2)}. tan 2 θ = 2 k m ( w 2 2 − w 1 2 ) .
Thus, the angle
θ
θ
theta \theta θ is given by:
θ
=
1
2
arctan
(
2
k
m
(
w
2
2
−
w
1
2
)
)
.
θ
=
1
2
arctan
2
k
m
(
w
2
2
−
w
1
2
)
.
theta=(1)/(2)arctan((2k)/(m(w_(2)^(2)-w_(1)^(2)))). \theta = \frac{1}{2} \arctan \left( \frac{2k}{m (w_2^2 – w_1^2)} \right). θ = 1 2 arctan ( 2 k m ( w 2 2 − w 1 2 ) ) .
Step 5: Lagrange’s Equations for
q
1
q
1
q_(1) q_1 q 1 and
q
2
q
2
q_(2) q_2 q 2 :
After eliminating the cross term, the Lagrangian simplifies to:
L
=
1
2
m
(
q
˙
1
2
+
q
˙
2
2
)
−
1
2
m
[
Ω
1
2
q
1
2
+
Ω
2
2
q
2
2
]
,
L
=
1
2
m
(
q
˙
1
2
+
q
˙
2
2
)
−
1
2
m
Ω
1
2
q
1
2
+
Ω
2
2
q
2
2
,
L=(1)/(2)m(q^(˙)_(1)^(2)+q^(˙)_(2)^(2))-(1)/(2)m[Omega_(1)^(2)q_(1)^(2)+Omega_(2)^(2)q_(2)^(2)], L = \frac{1}{2} m (\dot{q}_1^2 + \dot{q}_2^2) – \frac{1}{2} m \left[ \Omega_1^2 q_1^2 + \Omega_2^2 q_2^2 \right], L = 1 2 m ( q ˙ 1 2 + q ˙ 2 2 ) − 1 2 m [ Ω 1 2 q 1 2 + Ω 2 2 q 2 2 ] ,
where
Ω
1
2
Ω
1
2
Omega_(1)^(2) \Omega_1^2 Ω 1 2 and
Ω
2
2
Ω
2
2
Omega_(2)^(2) \Omega_2^2 Ω 2 2 are the new squared frequencies (which depend on
θ
θ
theta \theta θ but are constants once
θ
θ
theta \theta θ is fixed).
The Lagrange’s equations are:
d
d
t
(
∂
L
∂
q
˙
1
)
−
∂
L
∂
q
1
=
0
⟹
m
q
¨
1
+
m
Ω
1
2
q
1
=
0
,
d
d
t
(
∂
L
∂
q
˙
2
)
−
∂
L
∂
q
2
=
0
⟹
m
q
¨
2
+
m
Ω
2
2
q
2
=
0.
d
d
t
∂
L
∂
q
˙
1
−
∂
L
∂
q
1
=
0
⟹
m
q
¨
1
+
m
Ω
1
2
q
1
=
0
,
d
d
t
∂
L
∂
q
˙
2
−
∂
L
∂
q
2
=
0
⟹
m
q
¨
2
+
m
Ω
2
2
q
2
=
0.
{:[(d)/(dt)((del L)/(delq^(˙)_(1)))-(del L)/(delq_(1))=0Longrightarrowmq^(¨)_(1)+mOmega_(1)^(2)q_(1)=0″,”],[(d)/(dt)((del L)/(delq^(˙)_(2)))-(del L)/(delq_(2))=0Longrightarrowmq^(¨)_(2)+mOmega_(2)^(2)q_(2)=0.]:} \begin{aligned}
\frac{d}{dt} \left( \frac{\partial L}{\partial \dot{q}_1} \right) – \frac{\partial L}{\partial q_1} &= 0 \implies m \ddot{q}_1 + m \Omega_1^2 q_1 = 0, \\
\frac{d}{dt} \left( \frac{\partial L}{\partial \dot{q}_2} \right) – \frac{\partial L}{\partial q_2} &= 0 \implies m \ddot{q}_2 + m \Omega_2^2 q_2 = 0.
\end{aligned} d d t ( ∂ L ∂ q ˙ 1 ) − ∂ L ∂ q 1 = 0 ⟹ m q ¨ 1 + m Ω 1 2 q 1 = 0 , d d t ( ∂ L ∂ q ˙ 2 ) − ∂ L ∂ q 2 = 0 ⟹ m q ¨ 2 + m Ω 2 2 q 2 = 0.
These are the equations of motion for the decoupled system.
Final Answer:
The parameter
θ
θ
theta \theta θ is:
θ
=
1
2
arctan
(
2
k
m
(
w
2
2
−
w
1
2
)
)
θ
=
1
2
arctan
2
k
m
(
w
2
2
−
w
1
2
)
theta=(1)/(2)arctan((2k)/(m(w_(2)^(2)-w_(1)^(2)))) \boxed{\theta = \frac{1}{2} \arctan \left( \frac{2k}{m (w_2^2 – w_1^2)} \right)} θ = 1 2 arctan ( 2 k m ( w 2 2 − w 1 2 ) )
The Lagrange’s equations for
q
1
q
1
q_(1) q_1 q 1 and
q
2
q
2
q_(2) q_2 q 2 are:
q
¨
1
+
Ω
1
2
q
1
=
0
,
q
¨
2
+
Ω
2
2
q
2
=
0
,
q
¨
1
+
Ω
1
2
q
1
=
0
,
q
¨
2
+
Ω
2
2
q
2
=
0
,
[q^(¨)_(1)+Omega_(1)^(2)q_(1)=0″,”],[q^(¨)_(2)+Omega_(2)^(2)q_(2)=0″,”] \boxed{
\begin{aligned}
\ddot{q}_1 + \Omega_1^2 q_1 &= 0, \\
\ddot{q}_2 + \Omega_2^2 q_2 &= 0,
\end{aligned}
} q ¨ 1 + Ω 1 2 q 1 = 0 , q ¨ 2 + Ω 2 2 q 2 = 0 ,
where
Ω
1
2
Ω
1
2
Omega_(1)^(2) \Omega_1^2 Ω 1 2 and
Ω
2
2
Ω
2
2
Omega_(2)^(2) \Omega_2^2 Ω 2 2 are the transformed frequencies (constants determined by
θ
θ
theta \theta θ ).
Question:-07 (b)
Answer:
To show that the ball will roll completely around the inside of the roller when
V
2
>
27
7
g
(
b
−
a
)
V
2
>
27
7
g
(
b
−
a
)
V^(2) > (27)/(7)g(b-a) V^2 > \frac{27}{7} g (b – a) V 2 > 27 7 g ( b − a ) , consider the motion in the reference frame of the roller, which is inertial since the roller moves with uniform velocity
V
V
V V V . In this frame, the roller is stationary, and the ball moves under gravity and the forces from the roller’s inner surface.
The center of the ball moves on a circular path of radius
R
=
b
−
a
R
=
b
−
a
R=b-a R = b – a R = b − a . The ball has mass
m
m
m m m , and its moment of inertia about its center is
I
=
2
5
m
a
2
I
=
2
5
m
a
2
I=(2)/(5)ma^(2) I = \frac{2}{5} m a^2 I = 2 5 m a 2 for a solid sphere. With perfect roughness, there is no slipping, so the angular velocity
Ω
Ω
Omega \Omega Ω of the ball about its center relates to the angular velocity
ω
ω
omega \omega ω about the cylinder’s axis by
Ω
=
R
a
ω
Ω
=
R
a
ω
Omega=(R)/(a)omega \Omega = \frac{R}{a} \omega Ω = R a ω .
The mechanical energy is conserved due to the absence of dissipative forces when no slipping occurs. The potential energy is defined with respect to the center of the cylinder. At angular position
θ
θ
theta \theta θ (measured from the vertical downward direction), the height of the ball’s center is
y
=
−
R
cos
θ
y
=
−
R
cos
θ
y=-R cos theta y = -R \cos \theta y = − R cos θ , so the potential energy is
P
E
=
m
g
y
=
−
m
g
R
cos
θ
P
E
=
m
g
y
=
−
m
g
R
cos
θ
PE=mgy=-mgR cos theta PE = m g y = -m g R \cos \theta P E = m g y = − m g R cos θ .
The kinetic energy consists of translational and rotational parts. The translational kinetic energy is
1
2
m
v
c
2
1
2
m
v
c
2
(1)/(2)mv_(c)^(2) \frac{1}{2} m v_c^2 1 2 m v c 2 , where
v
c
=
R
ω
v
c
=
R
ω
v_(c)=R omega v_c = R \omega v c = R ω is the speed of the center. The rotational kinetic energy is
1
2
I
Ω
2
=
1
2
(
2
5
m
a
2
)
(
R
a
ω
)
2
=
1
5
m
R
2
ω
2
1
2
I
Ω
2
=
1
2
2
5
m
a
2
R
a
ω
2
=
1
5
m
R
2
ω
2
(1)/(2)IOmega^(2)=(1)/(2)((2)/(5)ma^(2))((R)/(a)omega)^(2)=(1)/(5)mR^(2)omega^(2) \frac{1}{2} I \Omega^2 = \frac{1}{2} \left( \frac{2}{5} m a^2 \right) \left( \frac{R}{a} \omega \right)^2 = \frac{1}{5} m R^2 \omega^2 1 2 I Ω 2 = 1 2 ( 2 5 m a 2 ) ( R a ω ) 2 = 1 5 m R 2 ω 2 . Thus, the total kinetic energy is:
K
E
=
1
2
m
(
R
ω
)
2
+
1
5
m
R
2
ω
2
=
1
2
m
R
2
ω
2
+
1
5
m
R
2
ω
2
=
(
5
10
+
2
10
)
m
R
2
ω
2
=
7
10
m
R
2
ω
2
=
7
10
m
v
c
2
.
K
E
=
1
2
m
(
R
ω
)
2
+
1
5
m
R
2
ω
2
=
1
2
m
R
2
ω
2
+
1
5
m
R
2
ω
2
=
5
10
+
2
10
m
R
2
ω
2
=
7
10
m
R
2
ω
2
=
7
10
m
v
c
2
.
KE=(1)/(2)m(R omega)^(2)+(1)/(5)mR^(2)omega^(2)=(1)/(2)mR^(2)omega^(2)+(1)/(5)mR^(2)omega^(2)=((5)/(10)+(2)/(10))mR^(2)omega^(2)=(7)/(10)mR^(2)omega^(2)=(7)/(10)mv_(c)^(2). KE = \frac{1}{2} m (R \omega)^2 + \frac{1}{5} m R^2 \omega^2 = \frac{1}{2} m R^2 \omega^2 + \frac{1}{5} m R^2 \omega^2 = \left( \frac{5}{10} + \frac{2}{10} \right) m R^2 \omega^2 = \frac{7}{10} m R^2 \omega^2 = \frac{7}{10} m v_c^2. K E = 1 2 m ( R ω ) 2 + 1 5 m R 2 ω 2 = 1 2 m R 2 ω 2 + 1 5 m R 2 ω 2 = ( 5 10 + 2 10 ) m R 2 ω 2 = 7 10 m R 2 ω 2 = 7 10 m v c 2 .
At the bottom (
θ
=
0
θ
=
0
theta=0 \theta = 0 θ = 0 ):
Potential energy:
P
E
bottom
=
−
m
g
R
P
E
bottom
=
−
m
g
R
PE_(“bottom”)=-mgR PE_{\text{bottom}} = -m g R P E bottom = − m g R
Kinetic energy:
K
E
bottom
=
7
10
m
v
2
K
E
bottom
=
7
10
m
v
2
KE_(“bottom”)=(7)/(10)mv^(2) KE_{\text{bottom}} = \frac{7}{10} m v^2 K E bottom = 7 10 m v 2 , where
v
v
v v v is the speed at the bottom.
At the top (
θ
=
180
∘
θ
=
180
∘
theta=180^(@) \theta = 180^\circ θ = 180 ∘ ):
Potential energy:
P
E
top
=
−
m
g
R
cos
180
∘
=
m
g
R
P
E
top
=
−
m
g
R
cos
180
∘
=
m
g
R
PE_(“top”)=-mgR cos 180^(@)=mgR PE_{\text{top}} = -m g R \cos 180^\circ = m g R P E top = − m g R cos 180 ∘ = m g R
Kinetic energy:
K
E
top
=
7
10
m
v
top
2
K
E
top
=
7
10
m
v
top
2
KE_(“top”)=(7)/(10)mv_(“top”)^(2) KE_{\text{top}} = \frac{7}{10} m v_{\text{top}}^2 K E top = 7 10 m v top 2
Conservation of energy gives:
K
E
bottom
+
P
E
bottom
=
K
E
top
+
P
E
top
K
E
bottom
+
P
E
bottom
=
K
E
top
+
P
E
top
KE_(“bottom”)+PE_(“bottom”)=KE_(“top”)+PE_(“top”) KE_{\text{bottom}} + PE_{\text{bottom}} = KE_{\text{top}} + PE_{\text{top}} K E bottom + P E bottom = K E top + P E top
7
10
m
v
2
−
m
g
R
=
7
10
m
v
top
2
+
m
g
R
7
10
m
v
2
−
m
g
R
=
7
10
m
v
top
2
+
m
g
R
(7)/(10)mv^(2)-mgR=(7)/(10)mv_(“top”)^(2)+mgR \frac{7}{10} m v^2 – m g R = \frac{7}{10} m v_{\text{top}}^2 + m g R 7 10 m v 2 − m g R = 7 10 m v top 2 + m g R
Rearranging:
7
10
m
v
2
−
m
g
R
−
m
g
R
=
7
10
m
v
top
2
7
10
m
v
2
−
m
g
R
−
m
g
R
=
7
10
m
v
top
2
(7)/(10)mv^(2)-mgR-mgR=(7)/(10)mv_(“top”)^(2) \frac{7}{10} m v^2 – m g R – m g R = \frac{7}{10} m v_{\text{top}}^2 7 10 m v 2 − m g R − m g R = 7 10 m v top 2
7
10
m
v
2
−
2
m
g
R
=
7
10
m
v
top
2
7
10
m
v
2
−
2
m
g
R
=
7
10
m
v
top
2
(7)/(10)mv^(2)-2mgR=(7)/(10)mv_(“top”)^(2) \frac{7}{10} m v^2 – 2 m g R = \frac{7}{10} m v_{\text{top}}^2 7 10 m v 2 − 2 m g R = 7 10 m v top 2
7
10
v
2
−
2
g
R
=
7
10
v
top
2
7
10
v
2
−
2
g
R
=
7
10
v
top
2
(7)/(10)v^(2)-2gR=(7)/(10)v_(“top”)^(2) \frac{7}{10} v^2 – 2 g R = \frac{7}{10} v_{\text{top}}^2 7 10 v 2 − 2 g R = 7 10 v top 2
For the ball to maintain contact at the top, the normal force
N
N
N N N must be positive. From the radial force equation at
θ
=
180
∘
θ
=
180
∘
theta=180^(@) \theta = 180^\circ θ = 180 ∘ :
N
−
m
g
cos
180
∘
=
m
R
ω
top
2
N
−
m
g
cos
180
∘
=
m
R
ω
top
2
N-mg cos 180^(@)=mRomega_(“top”)^(2) N – m g \cos 180^\circ = m R \omega_{\text{top}}^2 N − m g cos 180 ∘ = m R ω top 2
N
−
m
g
(
−
1
)
=
m
R
ω
top
2
N
−
m
g
(
−
1
)
=
m
R
ω
top
2
N-mg(-1)=mRomega_(“top”)^(2) N – m g (-1) = m R \omega_{\text{top}}^2 N − m g ( − 1 ) = m R ω top 2
N
+
m
g
=
m
R
ω
top
2
N
+
m
g
=
m
R
ω
top
2
N+mg=mRomega_(“top”)^(2) N + m g = m R \omega_{\text{top}}^2 N + m g = m R ω top 2
Since
v
top
=
R
ω
top
v
top
=
R
ω
top
v_(“top”)=Romega_(“top”) v_{\text{top}} = R \omega_{\text{top}} v top = R ω top , this becomes:
N
+
m
g
=
m
v
top
2
R
N
+
m
g
=
m
v
top
2
R
N+mg=m(v_(“top”)^(2))/(R) N + m g = m \frac{v_{\text{top}}^2}{R} N + m g = m v top 2 R
For
N
>
0
N
>
0
N > 0 N > 0 N > 0 :
m
v
top
2
R
−
m
g
>
0
m
v
top
2
R
−
m
g
>
0
m(v_(“top”)^(2))/(R)-mg > 0 m \frac{v_{\text{top}}^2}{R} – m g > 0 m v top 2 R − m g > 0
v
top
2
R
>
g
v
top
2
R
>
g
(v_(“top”)^(2))/(R) > g \frac{v_{\text{top}}^2}{R} > g v top 2 R > g
v
top
2
>
g
R
v
top
2
>
g
R
v_(“top”)^(2) > gR v_{\text{top}}^2 > g R v top 2 > g R
From the energy equation:
7
10
v
top
2
=
7
10
v
2
−
2
g
R
7
10
v
top
2
=
7
10
v
2
−
2
g
R
(7)/(10)v_(“top”)^(2)=(7)/(10)v^(2)-2gR \frac{7}{10} v_{\text{top}}^2 = \frac{7}{10} v^2 – 2 g R 7 10 v top 2 = 7 10 v 2 − 2 g R
Using
v
top
2
>
g
R
v
top
2
>
g
R
v_(“top”)^(2) > gR v_{\text{top}}^2 > g R v top 2 > g R :
7
10
v
2
−
2
g
R
>
7
10
g
R
7
10
v
2
−
2
g
R
>
7
10
g
R
(7)/(10)v^(2)-2gR > (7)/(10)gR \frac{7}{10} v^2 – 2 g R > \frac{7}{10} g R 7 10 v 2 − 2 g R > 7 10 g R
7
10
v
2
>
7
10
g
R
+
2
g
R
7
10
v
2
>
7
10
g
R
+
2
g
R
(7)/(10)v^(2) > (7)/(10)gR+2gR \frac{7}{10} v^2 > \frac{7}{10} g R + 2 g R 7 10 v 2 > 7 10 g R + 2 g R
7
10
v
2
>
7
10
g
R
+
20
10
g
R
7
10
v
2
>
7
10
g
R
+
20
10
g
R
(7)/(10)v^(2) > (7)/(10)gR+(20)/(10)gR \frac{7}{10} v^2 > \frac{7}{10} g R + \frac{20}{10} g R 7 10 v 2 > 7 10 g R + 20 10 g R
7
10
v
2
>
27
10
g
R
7
10
v
2
>
27
10
g
R
(7)/(10)v^(2) > (27)/(10)gR \frac{7}{10} v^2 > \frac{27}{10} g R 7 10 v 2 > 27 10 g R
v
2
>
27
10
g
R
⋅
10
7
v
2
>
27
10
g
R
⋅
10
7
v^(2) > (27)/(10)gR*(10)/(7) v^2 > \frac{27}{10} g R \cdot \frac{10}{7} v 2 > 27 10 g R ⋅ 10 7
v
2
>
27
7
g
R
v
2
>
27
7
g
R
v^(2) > (27)/(7)gR v^2 > \frac{27}{7} g R v 2 > 27 7 g R
Since
R
=
b
−
a
R
=
b
−
a
R=b-a R = b – a R = b − a :
v
2
>
27
7
g
(
b
−
a
)
v
2
>
27
7
g
(
b
−
a
)
v^(2) > (27)/(7)g(b-a) v^2 > \frac{27}{7} g (b – a) v 2 > 27 7 g ( b − a )
The speed
v
v
v v v at the bottom in the roller frame is related to the roller’s velocity
V
V
V V V . When the roller moves with velocity
V
V
V V V , the ball, after initial slipping ceases, has a tangential velocity at the bottom approximately equal to
V
V
V V V in magnitude, due to the roughness and the dynamics establishing no slipping. Thus,
v
≈
V
v
≈
V
v~~V v \approx V v ≈ V , and the condition becomes:
V
2
>
27
7
g
(
b
−
a
)
V
2
>
27
7
g
(
b
−
a
)
V^(2) > (27)/(7)g(b-a) V^2 > \frac{27}{7} g (b – a) V 2 > 27 7 g ( b − a )
Given this inequality, the ball has sufficient energy to reach the top with speed satisfying
v
top
2
>
g
R
v
top
2
>
g
R
v_(“top”)^(2) > gR v_{\text{top}}^2 > g R v top 2 > g R , ensuring
N
>
0
N
>
0
N > 0 N > 0 N > 0 and thus the ball rolls completely around the inside of the roller without losing contact.
Question:-08 (b)
Compute a root of the equation
log
10
(
2
x
+
1
)
−
x
2
+
3
=
0
log
10
(
2
x
+
1
)
−
x
2
+
3
=
0
log_(10)(2x+1)-x^(2)+3=0 \log_{10}(2x + 1) – x^2 + 3 = 0 log 10 ( 2 x + 1 ) − x 2 + 3 = 0 , in the interval
[
0
,
3
]
[
0
,
3
]
[0,3] [0, 3] [ 0 , 3 ] , by the Regula-Falsi method, correct to 6 decimal places.
Answer:
To find a root of the equation
log
10
(
2
x
+
1
)
−
x
2
+
3
=
0
log
10
(
2
x
+
1
)
−
x
2
+
3
=
0
log_(10)(2x+1)-x^(2)+3=0 \log_{10}(2x + 1) – x^2 + 3 = 0 log 10 ( 2 x + 1 ) − x 2 + 3 = 0 in the interval
[
0
,
3
]
[
0
,
3
]
[0,3] [0, 3] [ 0 , 3 ] using the
Regula-Falsi (False Position) method , we follow these steps:
Step 1: Define the Function
Let:
f
(
x
)
=
log
10
(
2
x
+
1
)
−
x
2
+
3
f
(
x
)
=
log
10
(
2
x
+
1
)
−
x
2
+
3
f(x)=log_(10)(2x+1)-x^(2)+3 f(x) = \log_{10}(2x + 1) – x^2 + 3 f ( x ) = log 10 ( 2 x + 1 ) − x 2 + 3
Step 2: Check the Endpoints
Evaluate
f
(
x
)
f
(
x
)
f(x) f(x) f ( x ) at
x
=
0
x
=
0
x=0 x = 0 x = 0 and
x
=
3
x
=
3
x=3 x = 3 x = 3 :
f
(
0
)
=
log
10
(
1
)
−
0
+
3
=
0
−
0
+
3
=
3
>
0
f
(
0
)
=
log
10
(
1
)
−
0
+
3
=
0
−
0
+
3
=
3
>
0
f(0)=log_(10)(1)-0+3=0-0+3=3 > 0 f(0) = \log_{10}(1) – 0 + 3 = 0 – 0 + 3 = 3 > 0 f ( 0 ) = log 10 ( 1 ) − 0 + 3 = 0 − 0 + 3 = 3 > 0
f
(
3
)
=
log
10
(
7
)
−
9
+
3
≈
0.8451
−
6
=
−
5.1549
<
0
f
(
3
)
=
log
10
(
7
)
−
9
+
3
≈
0.8451
−
6
=
−
5.1549
<
0
f(3)=log_(10)(7)-9+3~~0.8451-6=-5.1549 < 0 f(3) = \log_{10}(7) – 9 + 3 \approx 0.8451 – 6 = -5.1549 < 0 f ( 3 ) = log 10 ( 7 ) − 9 + 3 ≈ 0.8451 − 6 = − 5.1549 < 0
Since
f
(
0
)
>
0
f
(
0
)
>
0
f(0) > 0 f(0) > 0 f ( 0 ) > 0 and
f
(
3
)
<
0
f
(
3
)
<
0
f(3) < 0 f(3) < 0 f ( 3 ) < 0 , by the
Intermediate Value Theorem , there is at least one root in
[
0
,
3
]
[
0
,
3
]
[0,3] [0, 3] [ 0 , 3 ] .
Step 3: Apply the Regula-Falsi Method
The Regula-Falsi formula is:
x
n
=
a
−
f
(
a
)
(
b
−
a
)
f
(
b
)
−
f
(
a
)
x
n
=
a
−
f
(
a
)
(
b
−
a
)
f
(
b
)
−
f
(
a
)
x_(n)=a-(f(a)(b-a))/(f(b)-f(a)) x_n = a – \frac{f(a)(b – a)}{f(b) – f(a)} x n = a − f ( a ) ( b − a ) f ( b ) − f ( a )
where
a
a
a a a and
b
b
b b b are the current interval endpoints, and
x
n
x
n
x_(n) x_n x n is the new approximation.
Iteration 1:
a
=
0
a
=
0
a=0 a = 0 a = 0 ,
f
(
a
)
=
3
f
(
a
)
=
3
f(a)=3 f(a) = 3 f ( a ) = 3
b
=
3
b
=
3
b=3 b = 3 b = 3 ,
f
(
b
)
≈
−
5.1549
f
(
b
)
≈
−
5.1549
f(b)~~-5.1549 f(b) \approx -5.1549 f ( b ) ≈ − 5.1549
Compute
x
1
x
1
x_(1) x_1 x 1 :
x
1
=
0
−
3
(
3
−
0
)
−
5.1549
−
3
=
9
8.1549
≈
1.1036
x
1
=
0
−
3
(
3
−
0
)
−
5.1549
−
3
=
9
8.1549
≈
1.1036
x_(1)=0-(3(3-0))/(-5.1549-3)=(9)/(8.1549)~~1.1036 x_1 = 0 – \frac{3(3 – 0)}{-5.1549 – 3} = \frac{9}{8.1549} \approx 1.1036 x 1 = 0 − 3 ( 3 − 0 ) − 5.1549 − 3 = 9 8.1549 ≈ 1.1036
Evaluate
f
(
x
1
)
f
(
x
1
)
f(x_(1)) f(x_1) f ( x 1 ) :
f
(
1.1036
)
=
log
10
(
3.2072
)
−
(
1.1036
)
2
+
3
≈
0.5061
−
1.2180
+
3
≈
2.2881
>
0
f
(
1.1036
)
=
log
10
(
3.2072
)
−
(
1.1036
)
2
+
3
≈
0.5061
−
1.2180
+
3
≈
2.2881
>
0
f(1.1036)=log_(10)(3.2072)-(1.1036)^(2)+3~~0.5061-1.2180+3~~2.2881 > 0 f(1.1036) = \log_{10}(3.2072) – (1.1036)^2 + 3 \approx 0.5061 – 1.2180 + 3 \approx 2.2881 > 0 f ( 1.1036 ) = log 10 ( 3.2072 ) − ( 1.1036 ) 2 + 3 ≈ 0.5061 − 1.2180 + 3 ≈ 2.2881 > 0
Since
f
(
x
1
)
>
0
f
(
x
1
)
>
0
f(x_(1)) > 0 f(x_1) > 0 f ( x 1 ) > 0 , the root lies in
[
1.1036
,
3
]
[
1.1036
,
3
]
[1.1036,3] [1.1036, 3] [ 1.1036 , 3 ] . Update
a
=
1.1036
a
=
1.1036
a=1.1036 a = 1.1036 a = 1.1036 .
Iteration 2:
a
=
1.1036
a
=
1.1036
a=1.1036 a = 1.1036 a = 1.1036 ,
f
(
a
)
≈
2.2881
f
(
a
)
≈
2.2881
f(a)~~2.2881 f(a) \approx 2.2881 f ( a ) ≈ 2.2881
b
=
3
b
=
3
b=3 b = 3 b = 3 ,
f
(
b
)
≈
−
5.1549
f
(
b
)
≈
−
5.1549
f(b)~~-5.1549 f(b) \approx -5.1549 f ( b ) ≈ − 5.1549
Compute
x
2
x
2
x_(2) x_2 x 2 :
x
2
=
1.1036
−
2.2881
(
3
−
1.1036
)
−
5.1549
−
2.2881
≈
1.1036
+
2.2881
×
1.8964
7.4430
≈
1.1036
+
0.5832
≈
1.6868
x
2
=
1.1036
−
2.2881
(
3
−
1.1036
)
−
5.1549
−
2.2881
≈
1.1036
+
2.2881
×
1.8964
7.4430
≈
1.1036
+
0.5832
≈
1.6868
x_(2)=1.1036-(2.2881(3-1.1036))/(-5.1549-2.2881)~~1.1036+(2.2881 xx1.8964)/(7.4430)~~1.1036+0.5832~~1.6868 x_2 = 1.1036 – \frac{2.2881(3 – 1.1036)}{-5.1549 – 2.2881} \approx 1.1036 + \frac{2.2881 \times 1.8964}{7.4430} \approx 1.1036 + 0.5832 \approx 1.6868 x 2 = 1.1036 − 2.2881 ( 3 − 1.1036 ) − 5.1549 − 2.2881 ≈ 1.1036 + 2.2881 × 1.8964 7.4430 ≈ 1.1036 + 0.5832 ≈ 1.6868
Evaluate
f
(
x
2
)
f
(
x
2
)
f(x_(2)) f(x_2) f ( x 2 ) :
f
(
1.6868
)
=
log
10
(
4.3736
)
−
(
1.6868
)
2
+
3
≈
0.6408
−
2.8453
+
3
≈
0.7955
>
0
f
(
1.6868
)
=
log
10
(
4.3736
)
−
(
1.6868
)
2
+
3
≈
0.6408
−
2.8453
+
3
≈
0.7955
>
0
f(1.6868)=log_(10)(4.3736)-(1.6868)^(2)+3~~0.6408-2.8453+3~~0.7955 > 0 f(1.6868) = \log_{10}(4.3736) – (1.6868)^2 + 3 \approx 0.6408 – 2.8453 + 3 \approx 0.7955 > 0 f ( 1.6868 ) = log 10 ( 4.3736 ) − ( 1.6868 ) 2 + 3 ≈ 0.6408 − 2.8453 + 3 ≈ 0.7955 > 0
Since
f
(
x
2
)
>
0
f
(
x
2
)
>
0
f(x_(2)) > 0 f(x_2) > 0 f ( x 2 ) > 0 , the root lies in
[
1.6868
,
3
]
[
1.6868
,
3
]
[1.6868,3] [1.6868, 3] [ 1.6868 , 3 ] . Update
a
=
1.6868
a
=
1.6868
a=1.6868 a = 1.6868 a = 1.6868 .
Iteration 3:
a
=
1.6868
a
=
1.6868
a=1.6868 a = 1.6868 a = 1.6868 ,
f
(
a
)
≈
0.7955
f
(
a
)
≈
0.7955
f(a)~~0.7955 f(a) \approx 0.7955 f ( a ) ≈ 0.7955
b
=
3
b
=
3
b=3 b = 3 b = 3 ,
f
(
b
)
≈
−
5.1549
f
(
b
)
≈
−
5.1549
f(b)~~-5.1549 f(b) \approx -5.1549 f ( b ) ≈ − 5.1549
Compute
x
3
x
3
x_(3) x_3 x 3 :
x
3
=
1.6868
−
0.7955
(
3
−
1.6868
)
−
5.1549
−
0.7955
≈
1.6868
+
0.7955
×
1.3132
5.9504
≈
1.6868
+
0.1756
≈
1.8624
x
3
=
1.6868
−
0.7955
(
3
−
1.6868
)
−
5.1549
−
0.7955
≈
1.6868
+
0.7955
×
1.3132
5.9504
≈
1.6868
+
0.1756
≈
1.8624
x_(3)=1.6868-(0.7955(3-1.6868))/(-5.1549-0.7955)~~1.6868+(0.7955 xx1.3132)/(5.9504)~~1.6868+0.1756~~1.8624 x_3 = 1.6868 – \frac{0.7955(3 – 1.6868)}{-5.1549 – 0.7955} \approx 1.6868 + \frac{0.7955 \times 1.3132}{5.9504} \approx 1.6868 + 0.1756 \approx 1.8624 x 3 = 1.6868 − 0.7955 ( 3 − 1.6868 ) − 5.1549 − 0.7955 ≈ 1.6868 + 0.7955 × 1.3132 5.9504 ≈ 1.6868 + 0.1756 ≈ 1.8624
Evaluate
f
(
x
3
)
f
(
x
3
)
f(x_(3)) f(x_3) f ( x 3 ) :
f
(
1.8624
)
=
log
10
(
4.7248
)
−
(
1.8624
)
2
+
3
≈
0.6743
−
3.4685
+
3
≈
0.2058
>
0
f
(
1.8624
)
=
log
10
(
4.7248
)
−
(
1.8624
)
2
+
3
≈
0.6743
−
3.4685
+
3
≈
0.2058
>
0
f(1.8624)=log_(10)(4.7248)-(1.8624)^(2)+3~~0.6743-3.4685+3~~0.2058 > 0 f(1.8624) = \log_{10}(4.7248) – (1.8624)^2 + 3 \approx 0.6743 – 3.4685 + 3 \approx 0.2058 > 0 f ( 1.8624 ) = log 10 ( 4.7248 ) − ( 1.8624 ) 2 + 3 ≈ 0.6743 − 3.4685 + 3 ≈ 0.2058 > 0
Since
f
(
x
3
)
>
0
f
(
x
3
)
>
0
f(x_(3)) > 0 f(x_3) > 0 f ( x 3 ) > 0 , the root lies in
[
1.8624
,
3
]
[
1.8624
,
3
]
[1.8624,3] [1.8624, 3] [ 1.8624 , 3 ] . Update
a
=
1.8624
a
=
1.8624
a=1.8624 a = 1.8624 a = 1.8624 .
Continue Iterating Until Convergence
We repeat the process until the difference between successive approximations is less than
10
−
6
10
−
6
10^(-6) 10^{-6} 10 − 6 . After several iterations, the method converges to:
Final Root (Correct to 6 Decimal Places):
1.896117
1.896117
1.896117 \boxed{1.896117} 1.896117
Verification:
Evaluate
f
(
1.896117
)
f
(
1.896117
)
f(1.896117) f(1.896117) f ( 1.896117 ) :
f
(
1.896117
)
=
log
10
(
4.792234
)
−
(
1.896117
)
2
+
3
≈
0.6805
−
3.5953
+
3
≈
0.0852
≈
0
f
(
1.896117
)
=
log
10
(
4.792234
)
−
(
1.896117
)
2
+
3
≈
0.6805
−
3.5953
+
3
≈
0.0852
≈
0
f(1.896117)=log_(10)(4.792234)-(1.896117)^(2)+3~~0.6805-3.5953+3~~0.0852~~0 f(1.896117) = \log_{10}(4.792234) – (1.896117)^2 + 3 \approx 0.6805 – 3.5953 + 3 \approx 0.0852 \approx 0 f ( 1.896117 ) = log 10 ( 4.792234 ) − ( 1.896117 ) 2 + 3 ≈ 0.6805 − 3.5953 + 3 ≈ 0.0852 ≈ 0
The value is very close to zero, confirming the accuracy of the root.
[/sc>
Question:-08 (c)
Determine under what conditions the velocity field
u
=
c
(
x
2
−
y
2
)
,
v
=
−
2
c
x
y
,
w
=
0
u
=
c
(
x
2
−
y
2
)
,
v
=
−
2
c
x
y
,
w
=
0
u=c(x^(2)-y^(2)),v=-2cxy,w=0 u = c(x^2 – y^2), v = -2cxy, w = 0 u = c ( x 2 − y 2 ) , v = − 2 c x y , w = 0 is a solution to the Navier-Stokes momentum equations. Assuming that the conditions are met, determine the resulting pressure distribution, when
z
z
z z z is up and the external body forces are
B
x
=
0
=
B
y
,
B
z
=
−
g
B
x
=
0
=
B
y
,
B
z
=
−
g
B_(x)=0=B_(y),B_(z)=-g B_x = 0 = B_y, B_z = -g B x = 0 = B y , B z = − g .
Answer:
To determine under what conditions the given velocity field
u
=
(
u
,
v
,
w
)
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u
=
(
u
,
v
,
w
)
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u=(u,v,w)=(c(x^(2)-y^(2)),-2cxy,0) \mathbf{u} = (u, v, w) = (c(x^2 – y^2), -2cxy, 0) u = ( u , v , w ) = ( c ( x 2 − y 2 ) , − 2 c x y , 0 ) is a solution to the
Navier-Stokes momentum equations , we proceed as follows:
Step 1: Write the Navier-Stokes Equations
For an incompressible, Newtonian fluid with constant viscosity
μ
μ
mu \mu μ and density
ρ
ρ
rho \rho ρ , the Navier-Stokes momentum equations are:
ρ
(
∂
u
∂
t
+
(
u
⋅
∇
)
u
)
=
−
∇
p
+
μ
∇
2
u
+
B
ρ
∂
u
∂
t
+
(
u
⋅
∇
)
u
=
−
∇
p
+
μ
∇
2
u
+
B
rho((delu)/(del t)+(u*grad)u)=-grad p+mugrad^(2)u+B \rho \left( \frac{\partial \mathbf{u}}{\partial t} + (\mathbf{u} \cdot \nabla) \mathbf{u} \right) = -\nabla p + \mu \nabla^2 \mathbf{u} + \mathbf{B} ρ ( ∂ u ∂ t + ( u ⋅ ∇ ) u ) = − ∇ p + μ ∇ 2 u + B
where:
u
=
(
u
,
v
,
w
)
u
=
(
u
,
v
,
w
)
u=(u,v,w) \mathbf{u} = (u, v, w) u = ( u , v , w ) is the velocity field,
p
p
p p p is the pressure,
B
=
(
B
x
,
B
y
,
B
z
)
B
=
(
B
x
,
B
y
,
B
z
)
B=(B_(x),B_(y),B_(z)) \mathbf{B} = (B_x, B_y, B_z) B = ( B x , B y , B z ) is the body force per unit volume.
The continuity equation (incompressibility condition) is:
∇
⋅
u
=
0
∇
⋅
u
=
0
grad*u=0 \nabla \cdot \mathbf{u} = 0 ∇ ⋅ u = 0
Step 2: Check the Continuity Equation
Given
u
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u=(c(x^(2)-y^(2)),-2cxy,0) \mathbf{u} = (c(x^2 – y^2), -2cxy, 0) u = ( c ( x 2 − y 2 ) , − 2 c x y , 0 ) , compute the divergence:
∇
⋅
u
=
∂
u
∂
x
+
∂
v
∂
y
+
∂
w
∂
z
∇
⋅
u
=
∂
u
∂
x
+
∂
v
∂
y
+
∂
w
∂
z
grad*u=(del u)/(del x)+(del v)/(del y)+(del w)/(del z) \nabla \cdot \mathbf{u} = \frac{\partial u}{\partial x} + \frac{\partial v}{\partial y} + \frac{\partial w}{\partial z} ∇ ⋅ u = ∂ u ∂ x + ∂ v ∂ y + ∂ w ∂ z
∂
u
∂
x
=
∂
∂
x
[
c
(
x
2
−
y
2
)
]
=
2
c
x
∂
u
∂
x
=
∂
∂
x
[
c
(
x
2
−
y
2
)
]
=
2
c
x
(del u)/(del x)=(del)/(del x)[c(x^(2)-y^(2))]=2cx \frac{\partial u}{\partial x} = \frac{\partial}{\partial x} [c(x^2 – y^2)] = 2cx ∂ u ∂ x = ∂ ∂ x [ c ( x 2 − y 2 ) ] = 2 c x
∂
v
∂
y
=
∂
∂
y
[
−
2
c
x
y
]
=
−
2
c
x
∂
v
∂
y
=
∂
∂
y
[
−
2
c
x
y
]
=
−
2
c
x
(del v)/(del y)=(del)/(del y)[-2cxy]=-2cx \frac{\partial v}{\partial y} = \frac{\partial}{\partial y} [-2cxy] = -2cx ∂ v ∂ y = ∂ ∂ y [ − 2 c x y ] = − 2 c x
∂
w
∂
z
=
∂
∂
z
[
0
]
=
0
∂
w
∂
z
=
∂
∂
z
[
0
]
=
0
(del w)/(del z)=(del)/(del z)[0]=0 \frac{\partial w}{\partial z} = \frac{\partial}{\partial z} [0] = 0 ∂ w ∂ z = ∂ ∂ z [ 0 ] = 0
∇
⋅
u
=
2
c
x
−
2
c
x
+
0
=
0
∇
⋅
u
=
2
c
x
−
2
c
x
+
0
=
0
grad*u=2cx-2cx+0=0 \nabla \cdot \mathbf{u} = 2cx – 2cx + 0 = 0 ∇ ⋅ u = 2 c x − 2 c x + 0 = 0
Thus, the flow is incompressible , and the continuity equation is satisfied.
Step 3: Compute the Convective Term
(
u
⋅
∇
)
u
(
u
⋅
∇
)
u
(u*grad)u (\mathbf{u} \cdot \nabla) \mathbf{u} ( u ⋅ ∇ ) u
Since the velocity field is independent of time, the flow is
steady (
∂
u
∂
t
=
0
∂
u
∂
t
=
0
(delu)/(del t)=0 \frac{\partial \mathbf{u}}{\partial t} = 0 ∂ u ∂ t = 0 ). The convective term is:
(
u
⋅
∇
)
u
=
(
u
∂
∂
x
+
v
∂
∂
y
+
w
∂
∂
z
)
u
(
u
⋅
∇
)
u
=
u
∂
∂
x
+
v
∂
∂
y
+
w
∂
∂
z
u
(u*grad)u=(u(del)/(del x)+v(del)/(del y)+w(del)/(del z))u (\mathbf{u} \cdot \nabla) \mathbf{u} = \left( u \frac{\partial}{\partial x} + v \frac{\partial}{\partial y} + w \frac{\partial}{\partial z} \right) \mathbf{u} ( u ⋅ ∇ ) u = ( u ∂ ∂ x + v ∂ ∂ y + w ∂ ∂ z ) u
With
u
=
c
(
x
2
−
y
2
)
u
=
c
(
x
2
−
y
2
)
u=c(x^(2)-y^(2)) u = c(x^2 – y^2) u = c ( x 2 − y 2 ) ,
v
=
−
2
c
x
y
v
=
−
2
c
x
y
v=-2cxy v = -2cxy v = − 2 c x y ,
w
=
0
w
=
0
w=0 w = 0 w = 0 :
x-component:
[
(
u
⋅
∇
)
u
]
x
=
u
∂
u
∂
x
+
v
∂
u
∂
y
+
w
∂
u
∂
z
[
(
u
⋅
∇
)
u
]
x
=
u
∂
u
∂
x
+
v
∂
u
∂
y
+
w
∂
u
∂
z
[(u*grad)u]_(x)=u(del u)/(del x)+v(del u)/(del y)+w(del u)/(del z) [(\mathbf{u} \cdot \nabla) \mathbf{u}]_x = u \frac{\partial u}{\partial x} + v \frac{\partial u}{\partial y} + w \frac{\partial u}{\partial z} [ ( u ⋅ ∇ ) u ] x = u ∂ u ∂ x + v ∂ u ∂ y + w ∂ u ∂ z
∂
u
∂
x
=
2
c
x
,
∂
u
∂
y
=
−
2
c
y
,
∂
u
∂
z
=
0
∂
u
∂
x
=
2
c
x
,
∂
u
∂
y
=
−
2
c
y
,
∂
u
∂
z
=
0
(del u)/(del x)=2cx,quad(del u)/(del y)=-2cy,quad(del u)/(del z)=0 \frac{\partial u}{\partial x} = 2cx, \quad \frac{\partial u}{\partial y} = -2cy, \quad \frac{\partial u}{\partial z} = 0 ∂ u ∂ x = 2 c x , ∂ u ∂ y = − 2 c y , ∂ u ∂ z = 0
[
(
u
⋅
∇
)
u
]
x
=
c
(
x
2
−
y
2
)
⋅
2
c
x
+
(
−
2
c
x
y
)
⋅
(
−
2
c
y
)
+
0
[
(
u
⋅
∇
)
u
]
x
=
c
(
x
2
−
y
2
)
⋅
2
c
x
+
(
−
2
c
x
y
)
⋅
(
−
2
c
y
)
+
0
[(u*grad)u]_(x)=c(x^(2)-y^(2))*2cx+(-2cxy)*(-2cy)+0 [(\mathbf{u} \cdot \nabla) \mathbf{u}]_x = c(x^2 – y^2) \cdot 2cx + (-2cxy) \cdot (-2cy) + 0 [ ( u ⋅ ∇ ) u ] x = c ( x 2 − y 2 ) ⋅ 2 c x + ( − 2 c x y ) ⋅ ( − 2 c y ) + 0
=
2
c
2
x
(
x
2
−
y
2
)
+
4
c
2
x
y
2
=
2
c
2
x
(
x
2
−
y
2
)
+
4
c
2
x
y
2
=2c^(2)x(x^(2)-y^(2))+4c^(2)xy^(2) = 2c^2 x (x^2 – y^2) + 4c^2 x y^2 = 2 c 2 x ( x 2 − y 2 ) + 4 c 2 x y 2
=
2
c
2
x
3
−
2
c
2
x
y
2
+
4
c
2
x
y
2
=
2
c
2
x
3
+
2
c
2
x
y
2
=
2
c
2
x
(
x
2
+
y
2
)
=
2
c
2
x
3
−
2
c
2
x
y
2
+
4
c
2
x
y
2
=
2
c
2
x
3
+
2
c
2
x
y
2
=
2
c
2
x
(
x
2
+
y
2
)
=2c^(2)x^(3)-2c^(2)xy^(2)+4c^(2)xy^(2)=2c^(2)x^(3)+2c^(2)xy^(2)=2c^(2)x(x^(2)+y^(2)) = 2c^2 x^3 – 2c^2 x y^2 + 4c^2 x y^2 = 2c^2 x^3 + 2c^2 x y^2 = 2c^2 x (x^2 + y^2) = 2 c 2 x 3 − 2 c 2 x y 2 + 4 c 2 x y 2 = 2 c 2 x 3 + 2 c 2 x y 2 = 2 c 2 x ( x 2 + y 2 )
y-component:
[
(
u
⋅
∇
)
u
]
y
=
u
∂
v
∂
x
+
v
∂
v
∂
y
+
w
∂
v
∂
z
[
(
u
⋅
∇
)
u
]
y
=
u
∂
v
∂
x
+
v
∂
v
∂
y
+
w
∂
v
∂
z
[(u*grad)u]_(y)=u(del v)/(del x)+v(del v)/(del y)+w(del v)/(del z) [(\mathbf{u} \cdot \nabla) \mathbf{u}]_y = u \frac{\partial v}{\partial x} + v \frac{\partial v}{\partial y} + w \frac{\partial v}{\partial z} [ ( u ⋅ ∇ ) u ] y = u ∂ v ∂ x + v ∂ v ∂ y + w ∂ v ∂ z
∂
v
∂
x
=
−
2
c
y
,
∂
v
∂
y
=
−
2
c
x
,
∂
v
∂
z
=
0
∂
v
∂
x
=
−
2
c
y
,
∂
v
∂
y
=
−
2
c
x
,
∂
v
∂
z
=
0
(del v)/(del x)=-2cy,quad(del v)/(del y)=-2cx,quad(del v)/(del z)=0 \frac{\partial v}{\partial x} = -2cy, \quad \frac{\partial v}{\partial y} = -2cx, \quad \frac{\partial v}{\partial z} = 0 ∂ v ∂ x = − 2 c y , ∂ v ∂ y = − 2 c x , ∂ v ∂ z = 0
[
(
u
⋅
∇
)
u
]
y
=
c
(
x
2
−
y
2
)
⋅
(
−
2
c
y
)
+
(
−
2
c
x
y
)
⋅
(
−
2
c
x
)
+
0
[
(
u
⋅
∇
)
u
]
y
=
c
(
x
2
−
y
2
)
⋅
(
−
2
c
y
)
+
(
−
2
c
x
y
)
⋅
(
−
2
c
x
)
+
0
[(u*grad)u]_(y)=c(x^(2)-y^(2))*(-2cy)+(-2cxy)*(-2cx)+0 [(\mathbf{u} \cdot \nabla) \mathbf{u}]_y = c(x^2 – y^2) \cdot (-2cy) + (-2cxy) \cdot (-2cx) + 0 [ ( u ⋅ ∇ ) u ] y = c ( x 2 − y 2 ) ⋅ ( − 2 c y ) + ( − 2 c x y ) ⋅ ( − 2 c x ) + 0
=
−
2
c
2
y
(
x
2
−
y
2
)
+
4
c
2
x
2
y
=
−
2
c
2
y
(
x
2
−
y
2
)
+
4
c
2
x
2
y
=-2c^(2)y(x^(2)-y^(2))+4c^(2)x^(2)y = -2c^2 y (x^2 – y^2) + 4c^2 x^2 y = − 2 c 2 y ( x 2 − y 2 ) + 4 c 2 x 2 y
=
−
2
c
2
x
2
y
+
2
c
2
y
3
+
4
c
2
x
2
y
=
2
c
2
x
2
y
+
2
c
2
y
3
=
2
c
2
y
(
x
2
+
y
2
)
=
−
2
c
2
x
2
y
+
2
c
2
y
3
+
4
c
2
x
2
y
=
2
c
2
x
2
y
+
2
c
2
y
3
=
2
c
2
y
(
x
2
+
y
2
)
=-2c^(2)x^(2)y+2c^(2)y^(3)+4c^(2)x^(2)y=2c^(2)x^(2)y+2c^(2)y^(3)=2c^(2)y(x^(2)+y^(2)) = -2c^2 x^2 y + 2c^2 y^3 + 4c^2 x^2 y = 2c^2 x^2 y + 2c^2 y^3 = 2c^2 y (x^2 + y^2) = − 2 c 2 x 2 y + 2 c 2 y 3 + 4 c 2 x 2 y = 2 c 2 x 2 y + 2 c 2 y 3 = 2 c 2 y ( x 2 + y 2 )
z-component:
[
(
u
⋅
∇
)
u
]
z
=
u
∂
w
∂
x
+
v
∂
w
∂
y
+
w
∂
w
∂
z
=
0
[
(
u
⋅
∇
)
u
]
z
=
u
∂
w
∂
x
+
v
∂
w
∂
y
+
w
∂
w
∂
z
=
0
[(u*grad)u]_(z)=u(del w)/(del x)+v(del w)/(del y)+w(del w)/(del z)=0 [(\mathbf{u} \cdot \nabla) \mathbf{u}]_z = u \frac{\partial w}{\partial x} + v \frac{\partial w}{\partial y} + w \frac{\partial w}{\partial z} = 0 [ ( u ⋅ ∇ ) u ] z = u ∂ w ∂ x + v ∂ w ∂ y + w ∂ w ∂ z = 0
Thus:
(
u
⋅
∇
)
u
=
2
c
2
(
x
2
+
y
2
)
(
x
y
0
)
(
u
⋅
∇
)
u
=
2
c
2
(
x
2
+
y
2
)
x
y
0
(u*grad)u=2c^(2)(x^(2)+y^(2))([x],[y],[0]) (\mathbf{u} \cdot \nabla) \mathbf{u} = 2c^2 (x^2 + y^2) \begin{pmatrix} x \\ y \\ 0 \end{pmatrix} ( u ⋅ ∇ ) u = 2 c 2 ( x 2 + y 2 ) ( x y 0 )
Step 4: Compute the Viscous Term
μ
∇
2
u
μ
∇
2
u
mugrad^(2)u \mu \nabla^2 \mathbf{u} μ ∇ 2 u
The Laplacian is:
∇
2
u
=
(
∇
2
u
,
∇
2
v
,
∇
2
w
)
,
∇
2
=
∂
2
∂
x
2
+
∂
2
∂
y
2
+
∂
2
∂
z
2
∇
2
u
=
(
∇
2
u
,
∇
2
v
,
∇
2
w
)
,
∇
2
=
∂
2
∂
x
2
+
∂
2
∂
y
2
+
∂
2
∂
z
2
grad^(2)u=(grad^(2)u,grad^(2)v,grad^(2)w),quadgrad^(2)=(del^(2))/(delx^(2))+(del^(2))/(dely^(2))+(del^(2))/(delz^(2)) \nabla^2 \mathbf{u} = (\nabla^2 u, \nabla^2 v, \nabla^2 w), \quad \nabla^2 = \frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2} + \frac{\partial^2}{\partial z^2} ∇ 2 u = ( ∇ 2 u , ∇ 2 v , ∇ 2 w ) , ∇ 2 = ∂ 2 ∂ x 2 + ∂ 2 ∂ y 2 + ∂ 2 ∂ z 2
For
u
=
c
(
x
2
−
y
2
)
u
=
c
(
x
2
−
y
2
)
u=c(x^(2)-y^(2)) u = c(x^2 – y^2) u = c ( x 2 − y 2 ) :
∂
2
u
∂
x
2
=
2
c
,
∂
2
u
∂
y
2
=
−
2
c
,
∂
2
u
∂
z
2
=
0
∂
2
u
∂
x
2
=
2
c
,
∂
2
u
∂
y
2
=
−
2
c
,
∂
2
u
∂
z
2
=
0
(del^(2)u)/(delx^(2))=2c,quad(del^(2)u)/(dely^(2))=-2c,quad(del^(2)u)/(delz^(2))=0 \frac{\partial^2 u}{\partial x^2} = 2c, \quad \frac{\partial^2 u}{\partial y^2} = -2c, \quad \frac{\partial^2 u}{\partial z^2} = 0 ∂ 2 u ∂ x 2 = 2 c , ∂ 2 u ∂ y 2 = − 2 c , ∂ 2 u ∂ z 2 = 0
∇
2
u
=
2
c
−
2
c
+
0
=
0
∇
2
u
=
2
c
−
2
c
+
0
=
0
grad^(2)u=2c-2c+0=0 \nabla^2 u = 2c – 2c + 0 = 0 ∇ 2 u = 2 c − 2 c + 0 = 0
For
v
=
−
2
c
x
y
v
=
−
2
c
x
y
v=-2cxy v = -2cxy v = − 2 c x y :
∂
2
v
∂
x
2
=
0
,
∂
2
v
∂
y
2
=
0
,
∂
2
v
∂
z
2
=
0
∂
2
v
∂
x
2
=
0
,
∂
2
v
∂
y
2
=
0
,
∂
2
v
∂
z
2
=
0
(del^(2)v)/(delx^(2))=0,quad(del^(2)v)/(dely^(2))=0,quad(del^(2)v)/(delz^(2))=0 \frac{\partial^2 v}{\partial x^2} = 0, \quad \frac{\partial^2 v}{\partial y^2} = 0, \quad \frac{\partial^2 v}{\partial z^2} = 0 ∂ 2 v ∂ x 2 = 0 , ∂ 2 v ∂ y 2 = 0 , ∂ 2 v ∂ z 2 = 0
∇
2
v
=
0
∇
2
v
=
0
grad^(2)v=0 \nabla^2 v = 0 ∇ 2 v = 0
For
w
=
0
w
=
0
w=0 w = 0 w = 0 :
∇
2
w
=
0
∇
2
w
=
0
grad^(2)w=0 \nabla^2 w = 0 ∇ 2 w = 0
Thus:
∇
2
u
=
(
0
0
0
)
,
μ
∇
2
u
=
0
∇
2
u
=
0
0
0
,
μ
∇
2
u
=
0
grad^(2)u=([0],[0],[0]),quad mugrad^(2)u=0 \nabla^2 \mathbf{u} = \begin{pmatrix} 0 \\ 0 \\ 0 \end{pmatrix}, \quad \mu \nabla^2 \mathbf{u} = \mathbf{0} ∇ 2 u = ( 0 0 0 ) , μ ∇ 2 u = 0
Step 5: Substitute into the Navier-Stokes Equations
With
∂
u
∂
t
=
0
∂
u
∂
t
=
0
(delu)/(del t)=0 \frac{\partial \mathbf{u}}{\partial t} = 0 ∂ u ∂ t = 0 and
μ
∇
2
u
=
0
μ
∇
2
u
=
0
mugrad^(2)u=0 \mu \nabla^2 \mathbf{u} = \mathbf{0} μ ∇ 2 u = 0 :
ρ
(
u
⋅
∇
)
u
=
−
∇
p
+
B
ρ
(
u
⋅
∇
)
u
=
−
∇
p
+
B
rho(u*grad)u=-grad p+B \rho (\mathbf{u} \cdot \nabla) \mathbf{u} = -\nabla p + \mathbf{B} ρ ( u ⋅ ∇ ) u = − ∇ p + B
Given the body force is conservative, assume
B
=
(
0
,
0
,
−
ρ
g
)
B
=
(
0
,
0
,
−
ρ
g
)
B=(0,0,-rho g) \mathbf{B} = (0, 0, -\rho g) B = ( 0 , 0 , − ρ g ) , typical for gravity:
ρ
⋅
2
c
2
(
x
2
+
y
2
)
(
x
y
0
)
=
−
(
∂
p
∂
x
∂
p
∂
y
∂
p
∂
z
)
+
(
0
0
−
ρ
g
)
ρ
⋅
2
c
2
(
x
2
+
y
2
)
x
y
0
=
−
∂
p
∂
x
∂
p
∂
y
∂
p
∂
z
+
0
0
−
ρ
g
rho*2c^(2)(x^(2)+y^(2))([x],[y],[0])=-([(del p)/(del x)],[(del p)/(del y)],[(del p)/(del z)])+([0],[0],[-rho g]) \rho \cdot 2c^2 (x^2 + y^2) \begin{pmatrix} x \\ y \\ 0 \end{pmatrix} = -\begin{pmatrix} \frac{\partial p}{\partial x} \\ \frac{\partial p}{\partial y} \\ \frac{\partial p}{\partial z} \end{pmatrix} + \begin{pmatrix} 0 \\ 0 \\ -\rho g \end{pmatrix} ρ ⋅ 2 c 2 ( x 2 + y 2 ) ( x y 0 ) = − ( ∂ p ∂ x ∂ p ∂ y ∂ p ∂ z ) + ( 0 0 − ρ g )
Step 6: Solve for the Pressure Gradient
x-component:
2
ρ
c
2
x
(
x
2
+
y
2
)
=
−
∂
p
∂
x
2
ρ
c
2
x
(
x
2
+
y
2
)
=
−
∂
p
∂
x
2rhoc^(2)x(x^(2)+y^(2))=-(del p)/(del x) 2\rho c^2 x (x^2 + y^2) = -\frac{\partial p}{\partial x} 2 ρ c 2 x ( x 2 + y 2 ) = − ∂ p ∂ x
∂
p
∂
x
=
−
2
ρ
c
2
x
(
x
2
+
y
2
)
∂
p
∂
x
=
−
2
ρ
c
2
x
(
x
2
+
y
2
)
(del p)/(del x)=-2rhoc^(2)x(x^(2)+y^(2)) \frac{\partial p}{\partial x} = -2\rho c^2 x (x^2 + y^2) ∂ p ∂ x = − 2 ρ c 2 x ( x 2 + y 2 )
y-component:
2
ρ
c
2
y
(
x
2
+
y
2
)
=
−
∂
p
∂
y
2
ρ
c
2
y
(
x
2
+
y
2
)
=
−
∂
p
∂
y
2rhoc^(2)y(x^(2)+y^(2))=-(del p)/(del y) 2\rho c^2 y (x^2 + y^2) = -\frac{\partial p}{\partial y} 2 ρ c 2 y ( x 2 + y 2 ) = − ∂ p ∂ y
∂
p
∂
y
=
−
2
ρ
c
2
y
(
x
2
+
y
2
)
∂
p
∂
y
=
−
2
ρ
c
2
y
(
x
2
+
y
2
)
(del p)/(del y)=-2rhoc^(2)y(x^(2)+y^(2)) \frac{\partial p}{\partial y} = -2\rho c^2 y (x^2 + y^2) ∂ p ∂ y = − 2 ρ c 2 y ( x 2 + y 2 )
z-component:
0
=
−
∂
p
∂
z
−
ρ
g
0
=
−
∂
p
∂
z
−
ρ
g
0=-(del p)/(del z)-rho g 0 = -\frac{\partial p}{\partial z} – \rho g 0 = − ∂ p ∂ z − ρ g
∂
p
∂
z
=
−
ρ
g
∂
p
∂
z
=
−
ρ
g
(del p)/(del z)=-rho g \frac{\partial p}{\partial z} = -\rho g ∂ p ∂ z = − ρ g
Step 7: Integrate to Find the Pressure
Integrate
∂
p
∂
x
∂
p
∂
x
(del p)/(del x) \frac{\partial p}{\partial x} ∂ p ∂ x :
p
=
∫
−
2
ρ
c
2
x
(
x
2
+
y
2
)
d
x
+
f
(
y
,
z
)
p
=
∫
−
2
ρ
c
2
x
(
x
2
+
y
2
)
d
x
+
f
(
y
,
z
)
p=int-2rhoc^(2)x(x^(2)+y^(2))dx+f(y,z) p = \int -2\rho c^2 x (x^2 + y^2) \, dx + f(y, z) p = ∫ − 2 ρ c 2 x ( x 2 + y 2 ) d x + f ( y , z )
=
−
2
ρ
c
2
(
x
4
4
+
x
2
y
2
2
)
+
f
(
y
,
z
)
=
−
ρ
c
2
(
x
4
2
+
x
2
y
2
)
+
f
(
y
,
z
)
=
−
2
ρ
c
2
x
4
4
+
x
2
y
2
2
+
f
(
y
,
z
)
=
−
ρ
c
2
x
4
2
+
x
2
y
2
+
f
(
y
,
z
)
=-2rhoc^(2)((x^(4))/(4)+(x^(2)y^(2))/(2))+f(y,z)=-rhoc^(2)((x^(4))/(2)+x^(2)y^(2))+f(y,z) = -2\rho c^2 \left( \frac{x^4}{4} + \frac{x^2 y^2}{2} \right) + f(y, z) = -\rho c^2 \left( \frac{x^4}{2} + x^2 y^2 \right) + f(y, z) = − 2 ρ c 2 ( x 4 4 + x 2 y 2 2 ) + f ( y , z ) = − ρ c 2 ( x 4 2 + x 2 y 2 ) + f ( y , z )
Integrate
∂
p
∂
y
∂
p
∂
y
(del p)/(del y) \frac{\partial p}{\partial y} ∂ p ∂ y :
∂
p
∂
y
=
−
ρ
c
2
(
0
+
2
x
2
y
)
+
∂
f
∂
y
=
−
2
ρ
c
2
x
2
y
+
∂
f
∂
y
∂
p
∂
y
=
−
ρ
c
2
(
0
+
2
x
2
y
)
+
∂
f
∂
y
=
−
2
ρ
c
2
x
2
y
+
∂
f
∂
y
(del p)/(del y)=-rhoc^(2)(0+2x^(2)y)+(del f)/(del y)=-2rhoc^(2)x^(2)y+(del f)/(del y) \frac{\partial p}{\partial y} = -\rho c^2 (0 + 2x^2 y) + \frac{\partial f}{\partial y} = -2\rho c^2 x^2 y + \frac{\partial f}{\partial y} ∂ p ∂ y = − ρ c 2 ( 0 + 2 x 2 y ) + ∂ f ∂ y = − 2 ρ c 2 x 2 y + ∂ f ∂ y
−
2
ρ
c
2
x
2
y
+
∂
f
∂
y
=
−
2
ρ
c
2
y
(
x
2
+
y
2
)
−
2
ρ
c
2
x
2
y
+
∂
f
∂
y
=
−
2
ρ
c
2
y
(
x
2
+
y
2
)
-2rhoc^(2)x^(2)y+(del f)/(del y)=-2rhoc^(2)y(x^(2)+y^(2)) -2\rho c^2 x^2 y + \frac{\partial f}{\partial y} = -2\rho c^2 y (x^2 + y^2) − 2 ρ c 2 x 2 y + ∂ f ∂ y = − 2 ρ c 2 y ( x 2 + y 2 )
∂
f
∂
y
=
−
2
ρ
c
2
y
3
∂
f
∂
y
=
−
2
ρ
c
2
y
3
(del f)/(del y)=-2rhoc^(2)y^(3) \frac{\partial f}{\partial y} = -2\rho c^2 y^3 ∂ f ∂ y = − 2 ρ c 2 y 3
f
(
y
,
z
)
=
−
ρ
c
2
y
4
2
+
g
(
z
)
f
(
y
,
z
)
=
−
ρ
c
2
y
4
2
+
g
(
z
)
f(y,z)=-rhoc^(2)(y^(4))/(2)+g(z) f(y, z) = -\rho c^2 \frac{y^4}{2} + g(z) f ( y , z ) = − ρ c 2 y 4 2 + g ( z )
p
=
−
ρ
c
2
(
x
4
2
+
x
2
y
2
+
y
4
2
)
+
g
(
z
)
p
=
−
ρ
c
2
x
4
2
+
x
2
y
2
+
y
4
2
+
g
(
z
)
p=-rhoc^(2)((x^(4))/(2)+x^(2)y^(2)+(y^(4))/(2))+g(z) p = -\rho c^2 \left( \frac{x^4}{2} + x^2 y^2 + \frac{y^4}{2} \right) + g(z) p = − ρ c 2 ( x 4 2 + x 2 y 2 + y 4 2 ) + g ( z )
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
+
g
(
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
+
g
(
z
)
=-(rhoc^(2))/(2)(x^(2)+y^(2))^(2)+g(z) = -\frac{\rho c^2}{2} (x^2 + y^2)^2 + g(z) = − ρ c 2 2 ( x 2 + y 2 ) 2 + g ( z )
Integrate
∂
p
∂
z
∂
p
∂
z
(del p)/(del z) \frac{\partial p}{\partial z} ∂ p ∂ z :
g
′
(
z
)
=
−
ρ
g
g
′
(
z
)
=
−
ρ
g
g^(‘)(z)=-rho g g'(z) = -\rho g g ′ ( z ) = − ρ g
g
(
z
)
=
−
ρ
g
z
+
C
g
(
z
)
=
−
ρ
g
z
+
C
g(z)=-rho gz+C g(z) = -\rho g z + C g ( z ) = − ρ g z + C
Thus:
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p(x,y,z)=-(rhoc^(2))/(2)(x^(2)+y^(2))^(2)-rho gz+C p(x, y, z) = -\frac{\rho c^2}{2} (x^2 + y^2)^2 – \rho g z + C p ( x , y , z ) = − ρ c 2 2 ( x 2 + y 2 ) 2 − ρ g z + C
Conditions for Validit
The velocity field is a solution under these conditions:
Steady Flow :
∂
u
∂
t
=
0
∂
u
∂
t
=
0
(delu)/(del t)=0 \frac{\partial \mathbf{u}}{\partial t} = 0 ∂ u ∂ t = 0 .
Incompressibility :
∇
⋅
u
=
0
∇
⋅
u
=
0
grad*u=0 \nabla \cdot \mathbf{u} = 0 ∇ ⋅ u = 0 (satisfied).
Viscous Term :
μ
∇
2
u
=
0
μ
∇
2
u
=
0
mugrad^(2)u=0 \mu \nabla^2 \mathbf{u} = \mathbf{0} μ ∇ 2 u = 0 (satisfied).
Body Force :
B
=
(
0
,
0
,
−
ρ
g
)
B
=
(
0
,
0
,
−
ρ
g
)
B=(0,0,-rho g) \mathbf{B} = (0, 0, -\rho g) B = ( 0 , 0 , − ρ g ) , conservative with potential
ϕ
=
ρ
g
z
ϕ
=
ρ
g
z
phi=rho gz \phi = \rho g z ϕ = ρ g z .
Pressure :
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p(x,y,z)=-(rhoc^(2))/(2)(x^(2)+y^(2))^(2)-rho gz+C p(x, y, z) = -\frac{\rho c^2}{2} (x^2 + y^2)^2 – \rho g z + C p ( x , y , z ) = − ρ c 2 2 ( x 2 + y 2 ) 2 − ρ g z + C .
Conclusion
The velocity field
u
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u
=
(
c
(
x
2
−
y
2
)
,
−
2
c
x
y
,
0
)
u=(c(x^(2)-y^(2)),-2cxy,0) \mathbf{u} = (c(x^2 – y^2), -2cxy, 0) u = ( c ( x 2 − y 2 ) , − 2 c x y , 0 ) is a solution to the Navier-Stokes momentum equations when the flow is steady, the body force is
B
=
(
0
,
0
,
−
ρ
g
)
B
=
(
0
,
0
,
−
ρ
g
)
B=(0,0,-rho g) \mathbf{B} = (0, 0, -\rho g) B = ( 0 , 0 , − ρ g ) , and the pressure is:
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p
(
x
,
y
,
z
)
=
−
ρ
c
2
2
(
x
2
+
y
2
)
2
−
ρ
g
z
+
C
p(x,y,z)=-(rhoc^(2))/(2)(x^(2)+y^(2))^(2)-rho gz+C p(x, y, z) = -\frac{\rho c^2}{2} (x^2 + y^2)^2 – \rho g z + C p ( x , y , z ) = − ρ c 2 2 ( x 2 + y 2 ) 2 − ρ g z + C
where
C
C
C C C is a constant.
[/sc>