Is Cauchy's integral formula applicable to this type of integral?

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Homework Help Overview

The discussion revolves around the applicability of Cauchy's integral formula to a specific integral involving a contour integral around the unit circle. The integral in question is \(\oint_{C}^{}{\frac{z^2+1}{e^{iz}-1}}\), and participants are exploring whether this integral can be evaluated using the formula or if an alternative method is necessary.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to determine if the integral can be expressed in a form suitable for Cauchy's integral formula, noting the presence of a pole at \(z=0\). Some participants suggest using the residue theorem instead, while others discuss the relationship between the residue theorem and Cauchy's integral formula.

Discussion Status

The discussion is active, with participants exploring different methods to evaluate the integral. Some guidance has been offered regarding the use of the residue theorem, but there is no explicit consensus on the best approach yet. Questions remain about the steps involved in applying these methods.

Contextual Notes

Participants mention that the original poster has not yet studied the residue theorem in their text, which may influence their understanding of the problem. There is also uncertainty about the steps required for the evaluation process, particularly regarding the Laurent expansion and residue calculation.

opticaltempest
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Homework Statement



I am trying to determine if Cauchy's integral formula will work on the following integral, where the contour C is the unit circle traversed in the counterclockwise direction.

\oint_{C}^{}{\frac{z^2+1}{e^{iz}-1}}


Homework Equations


See Cauchy's Integral Formula - http://en.wikipedia.org/wiki/Cauchy_integral_formula"

The Attempt at a Solution



I realize that there is a pole at z=0. I realize that if I could get this integral into the form

\frac{f(z)}{z},

with f(z) being analytic in and on the contour C, then I could use the formula. However, I'm not sure how to get the integrand in that form. Is it even possible to use Cauchy's integral formula on this integral, or do I need to use a different method to evaluate this integral?
 
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Ok, so it appears that I need to use the residue theorem in order to evaluate this integral. I was hoping I could just use the integral formula. I haven't got to study the residue theorem yet in my text. Thanks
 
The residue thorem is a simple use of the integral formula.
write f(z)=[z*f(z)]/z
 
so are these the steps:

do a laurent expansion of denominator
cancel with stuff in the numerator
then the coefficient of the z^{-1} term gives us the residue
multiply this by 2 \pi i to give the integral's value

im not too sure about the first of those two steps?
 

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