Riemann Zeta Function (Part 2, beware)

The Riemann zeta function states that for every $s$ ,

$\large \zeta (s) = \displaystyle \sum_{n=1}^\infty \frac {1}{n^{s}}$

Sometimes these sums are divergent but using analytic continuation, you can get a finite answer. Find $\zeta (0.5)$ .