Originally Posted by

**vincisonfire** This series

$\displaystyle 1 + \frac{cos(\theta)}{sin(\theta)} + \frac{cos(2\theta)}{sin^2(\theta)} + ... + \frac{cos(n\theta)}{sin^n(\theta)} $

I think that the summation notation would be $\displaystyle \sum_{i=0}^{n} \frac{cos(i\theta)}{sin^i(\theta)} $.

But anyway, I'm having trouble with the top one. I have tried to transform it so that I can use complex numbers to find the answer. I have not succeed. Does someone know the way (or any method) to do this problem?