The Fourier coefficients
b_n, n ≥ 1
for the function
f(x) = (x + 1)²
defined on the interval [- π, π] and by periodic extension outside of it, are:
a. ((-1)^n)/n²
b. 0
c. 4(-1)^n / n^2
d. - 4(-1)^n / n²
e. 2 /n²