The integral with complex variable in different path

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Evaluate $\oint_\gamma \frac{e^z}{z+5}\,{\rm d}z$ where

  1. $\gamma(t)=1+2e^{it},\,0\leq t\leq 2\pi$.

  2. $\gamma(t)=1+7e^{it},\,0\leq t\leq 2\pi$.

My method is by using Cauchy's integral formula, and let $f(z)=e^z$, then

$$\oint_\gamma \frac{e^z}{z+5}\,{\rm d}z = 2\pi if(-5)=2\pi i e^{-5}$$ What's the difference between 1. and 2.?

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Your answer for the second part is correct.

On the other hand, the circle $|z+1|=2$ given by the loop in part 1 does not contain -5. Therefore, CIF is non-applicable and the contour can be deformed to any point besides the problem at -5 (aka a pole of order 1 or simple pole), giving $0$.

On the other hand, the loop in part 2 is $|z+1|=7$, which contains -5. This forces you to use CIF.