SOLUTION
a) This function satisfies f (−x) = f (x) , therefore is an even function.
So the coefficients of the sine terms must vanish, i.e. b_n = 0.
Also note that the area under the function in the range −π ≤ x ≤π is zero,
which is obvious by inspecting the graph of the function. Therefore we also have a₀ = 0.