Help figuring out this trigometric substitution

  • Context: Graduate 
  • Thread starter Thread starter ComFlu945
  • Start date Start date
  • Tags Tags
    Substitution
Click For Summary
SUMMARY

The discussion focuses on the trigonometric substitution in complex analysis, specifically the expression for \( w \) involving \( u(x+iy) \) and the simplification of terms using polar coordinates. The key equations derived include \( N = x^2 - y^2 + k^2 \), \( M = 2xy \), and \( R^2 = (N^2 + M^2)^2 \). The final form of \( w \) is expressed as \( w = u(x+iy)(\cos(\theta/2) - i\sin(\theta/2))(R^2)^{-0.25} \), which simplifies the original complex expression significantly. The discussion clarifies the relationship between the variables and the use of polar coordinates in simplifying complex functions.

PREREQUISITES
  • Understanding of complex numbers and their representation in polar form
  • Familiarity with trigonometric identities and substitutions
  • Knowledge of calculus, specifically derivatives and integrals involving complex functions
  • Basic concepts of complex analysis, including the argument and modulus of complex numbers
NEXT STEPS
  • Study the properties of complex functions and their derivatives
  • Learn about polar coordinates and their applications in complex analysis
  • Explore trigonometric identities and their use in simplifying complex expressions
  • Investigate advanced topics in complex analysis, such as contour integration and residue theorem
USEFUL FOR

Mathematicians, physics students, and anyone studying complex analysis or seeking to understand trigonometric substitutions in mathematical expressions.

ComFlu945
Messages
9
Reaction score
0
From my notes I have

w=u(x+iy)*(x^2 - y^2 +k^2 + i(2xy))^-.5

We let N=x^2-y^2+k^2
M=2xy
R^2=(N^2+M^2)^2
theta=tan^-1(M/N)

using this, now

w=u(x+iy)*(cos(theta/2)-isin(theta/2))*(x^2 - y^2 +k^2 )^2 + (2xy)^2 )^-.25

I don't get that part. Btw, it simplifies to
w=u(x+iy)*(cos(theta/2)-isin(theta/2)*(R^2)^-.25
 
Physics news on Phys.org
This has nothing to do with "Abstract and Linear Algebra" so I am moving it to "General Math".
 
I haven't thought about that particular problem, but note that
(x+iy)^2=x^2-y^2+2ixy

So basically your equation is
\frac{u(z)}{\sqrt{z^2+k^2}}

It seems you used z^2+k^2=Re^{i\theta}[/tex] hence R=\abs{z^2+k^2} and \theta=\arg(z^2+k^2)
 
Last edited:
I figured it out. Let O=N+iM. Then let O=R*e^-i*theta
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
8K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 13 ·
Replies
13
Views
6K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K