This is a question regarding Fourier series.
∫ dx |f(x)|^2 = ∑ |Cn|2 (note the integral is between -π and π, and the sum is from n= -∞ to ∞)
Complex Fourier series: f(x) = ∑Cn einx (again between n = -∞ and ∞)
The Attempt at a Solution
So I figured the complex conjugate of the Fourier transform would be:
f*(x)= ∑ C*n e-inx
so |f(x)|2 = ∑ |Cn|2 (as the exponentials cancel)
But I don't understand how the integral comes into things? I think I'm just not overly good at manipulating summations etc, so any help would be greatly appreciated!