\sum\frac{\rho}{n}\ast\rho^{n}sin\sigma=\frac{1}{2}\asttan^{-1}\left(\frac{2*\rho*sin(\sigma)}{1-\rho^{2}}\right)\right)
this is a Fourier series listed in most references but I can't derive it. Any help?
I believe even though sin and cos are periodic over 2 pi a Fourier series is a representation over the given period and so the integrals must be taken over the period given. I forgot to multiply the integrals by \frac{1}{3\pi}