Fourier series in the interval  (0,2π) Problem 4  | Engineering Mathematics

Fourier series in the interval (0,2π) Problem 4 | Engineering Mathematics

Expand f(x) = x(2π-x) as Fourier series in the interval (0,2π). Hence deduce that the sum of 1/1^2 +1/2^2 +1/3^2 +1/4^2 …= π^2/6