# Homework Help: Use Cauchy Residue Theorem to find the integral

1. Sep 4, 2012

### DanniHuang

1. The problem statement, all variables and given/known data

To find the integral by Cauchy Residue Theorem and apply substitution method.

2. Relevant equations

To show: ∫$^{2∏}_{0}$$\frac{cosθ}{13+12cosθ}$=-$\frac{4∏}{15}$

3. The attempt at a solution
The solution I have done is attached. It is different as what the question wants me to show. I do not know where I did it wrong.

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2. Sep 4, 2012

### clamtrox

Otherwise it looks fine to me, except that
$$6z^3+13z^2+6z = 6 z(z+2/3)(z+3/2) \neq z(z+2/3)(z+3/2)$$