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How to show the following identity holds?

$ \displaystyle\sum_{n=1}^\infty\dfrac{2z}{z^2-n^2}=\pi\cot \pi z-\dfrac{1}{z}\qquad |z|<1 $

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    Glad it helped Américo. Cheers !2012-11-04

1 Answers 1

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I have found a link which deals with this problem: people.reed.edu/~jerry/311/cotan.pdf

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    Maybe they are expecting you to give a short description of the content in the paper, instead of just citing it. Regards.2013-06-11