Applying Cauchy's Integral Formula to Higher Power Denominators

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Discussion Overview

The discussion revolves around the application of Cauchy's Integral Formula to closed path integrals with higher power denominators. Participants explore how to handle integrals where the denominator includes terms raised to powers greater than one, particularly in the context of complex analysis.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions how to apply Cauchy's Integral Formula when the integral has a denominator raised to a power greater than one, specifically mentioning a form involving partial fractions.
  • Another participant clarifies that Cauchy's Integral Formula can be generalized to handle higher powers, providing the formula for the nth derivative of a function evaluated at a point.
  • A later reply acknowledges a mistake made in the initial post and indicates an intention to edit the original question.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the application of Cauchy's Integral Formula to the specific integral discussed, as the initial question remains unresolved while a clarification is provided.

Contextual Notes

The discussion does not fully resolve the implications of using partial fractions in the context of higher power denominators, nor does it clarify the specific conditions under which Cauchy's formula applies in this scenario.

Dissonance in E
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If i have a closed pathintegral of the form:
(sin(z)+3cos(z) + 3e^z)/((z-(pi/2)^2)
How is cauchys integral formula applicable? If I split the integral into partial fractions won't i still get A/(z-pi/2) + B/(z-pi/2)^2, the B part of which won't be applicable to cauchys formula since the denominator is still squared.

In short, how do i apply cauchys formula to integrals with a denominator with a power higher than 1.
 
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Apparently, by "Cauchy's formula" you are referring to
f(a)= \frac{1}{2\pi i}\cint_\gamma \frac{f(z)}{z- a} dz

However, it can be easily generalized to
f^{(n)}(a)= \frac{n!}{2\pi i}\cint_\gamma \frac{f(z)}{(z- a)^{n+1}}dz
where the left sided is the nth derivative of f evaluated at z= a.

In your case, that integral is equal to the derivative of f(z)= sin(z)+ 3cos(z)+ 3e^z evaluated at z= \pi/2, multiplied by 2\pi i.
 
Last edited by a moderator:
...multiplied by 2\pi i.
 
Right, thanks. I will now edit my post so I can pretend I didn't make that foolish mistake!
 

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