I have this question on my assignment:

Write the Fourier series for the 2-periodic function defined

as f(x) = |x| on [-1, 1] and then by choosing the correct value of x,

find the sum form j = 0 to infinity [1/(2j+1)^2].

Plot your result on the same axes as the

function to compare.

I got got the Fourier Series and have plotted them and compared them ez. But I'm not sure what the part about find the correct value of x to solve the sum is talking about. Please help.