What is the Fourier series of the periodic function f(t) = t^2 on the interval [-π, π]?

a) π^2/3 + 4π^2/π^2 cos(t) – 2π/π^2 cos(2t) + 4π^2/9π^2 cos(3t) – 2π/π^2 cos(4t) + …
b) π^2/3 + 4π^2/π^2 cos(t) – 2π/π^2 cos(2t) + 4π^2/9π^2 cos(3t) – 2π/9π^2 cos(4t) + …
c) π^2/3 + 4π^2/π^2 sin(t) – 2π/π^2 sin(2t) + 4π^2/9π^2 sin(3t) – 2π/π^2 sin(4t) + …
d) π^2/3 + 4π^2/π^2 sin(t) – 2π/π^2 sin(2t) + 4π^2/9π^2 sin(3t) – 2π/9π^2 sin(4t) + …

Answer: b) π^2/3 + 4π^2/π^2 cos