1. The problem statement, all variables and given/known data Hi all. Please take a look at the lowest equation in this picture: http://img143.imageshack.us/img143/744/picture2ao8.png This is Parselvals Identity. Let us say that I am given a Fourier series of f(x), and I want to calculate the integral of f(x)^2 from -L to L. In order to do this, I use Parsevals Identity. But the requirement for me to use Parsevals Identity is that the series is well-defined and square integrable. How do I show this?