Finding the sum of this p-series

[Theorγ]

Homework Statement

How do you find the sum of the p-series 1/n^2 from n = 1 to infinity? My friend asked me this question and I was completely stumped; I have no leads on what you are suppose to do to solve this. I would be glad if you guys could give me hints as to how to begin solving.

Homework Equations

Not sure what is used to solve this

The Attempt at a Solution

 

[LeonhardEuler]

This is called the Basel Problem, and it was first solved by Euler. There are several ways of solving it; I think the easiest is with a Fourier series. There are severla proofs here:
http://en.wikipedia.org/wiki/Basel_problem