Solve Complex Integral: \oint \frac{f(z)}{z^{2}+1}dz

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SUMMARY

The discussion focuses on evaluating the complex integral \(\oint \frac{f(z)}{z^{2}+1}dz\) over a circle \(\gamma_{r}\) centered at \(2i\) with varying radii. Participants identify the need to analyze three distinct cases based on the radius \(r\): \(03\). The conversation emphasizes the application of Cauchy's integral formula and the importance of handling singularities appropriately, particularly noting that if the contour passes through a singularity, the integral is defined in the principal value sense. The consensus is to approach the problem by breaking it into manageable cases rather than seeking a single comprehensive formula.

PREREQUISITES
  • Understanding of complex analysis, specifically Cauchy's integral formula.
  • Familiarity with contour integration and singularities in complex functions.
  • Knowledge of the behavior of integrals over different radii in the complex plane.
  • Ability to compute principal values of integrals involving singularities.
NEXT STEPS
  • Study Cauchy's integral formula in detail, focusing on its applications in complex analysis.
  • Learn about contour integration techniques and how to handle singularities effectively.
  • Research the concept of principal value integrals and their significance in complex analysis.
  • Explore examples of integrals over contours that pass through singularities for practical understanding.
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Students and professionals in mathematics, particularly those specializing in complex analysis, as well as anyone involved in solving complex integrals and understanding contour integration techniques.

strangequark
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Homework Statement


Let [tex]\gamma_{r}[/tex] be the circle centered at 2i with a radius r. Compute:

[tex]\oint \frac{f(z)}{z^{2}+1}dz[/tex]


Homework Equations



[tex]2 \pi i f(w)=\oint \frac{f(z)}{z-w}dz[/tex]

Cauchy's integral formula... maybe?

The Attempt at a Solution



I can see how to find solutions for two separate cases:

0<r<1
0<r<3
r>3

I have no idea how to find a general formula for this... nor am I sure what to do when [tex]\gamma[/tex] passes thru a singularity...

any help on how to get started would be MUCH appreciated... thanks in advance
 
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If the curve passes through the singularity then it's really only defined in the principle value sense. I wouldn't worry about that case. But you are doing it right. You have to split the answer into cases, not write on big formula.
 

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