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Math Help - please help!! (cauchy integral formula)

  1. #1
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    please help!! (cauchy integral formula)

    evaluate: f(z)=1/(z^4-1) with c:|z+1|=1 using cauchy's integral formula.




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  2. #2
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    Re: please help!! (cauchy integral formula)

    Well your contour is a circle of radius 1 centred at (-1, 0).

    Your function $\displaystyle \begin{align*} f(z) = \frac{1}{z^4 - 1} = \frac{1}{ \left( z^2 - 1 \right) \left( z^2 + 1 \right) } = \frac{1}{ \left( z - 1 \right) \left( z + 1 \right) \left( z - i \right) \left( z + i \right) } \end{align*}$.

    The top and bottom are both holomorphic, so there are simple poles at z = 1, -1, i, -i.

    Since only one of these lies inside the contour (z = -1), you can evaluate the integral using the Residue Theorem.
    Last edited by Prove It; May 15th 2014 at 02:58 AM.
    Thanks from baidyasuyam
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