Quick Q.

When dealing Fourier series Q's, $\displaystyle \cos(n \pi)$ is written as $\displaystyle (-1)^n$. What can $\displaystyle \cos (\frac{n \pi}{2})$ be written as? I might as well write out the equation i'm trying to simplify...

$\displaystyle -\frac{2T}{n \pi}( 2 \cos \frac{n \pi}{2} - 1 - \cos{n \pi} )$ = ?