Problem plot B2:

The function
       { -1  -Pi   < x < -Pi/4
g(x) = {  1  -Pi/4 < x <  Pi/4
       { -1   Pi/4 < x <  Pi
has fourier series. (Note the difference from plot B1).

Plot g and its best trig polynomial approx for N = 1, 2, 3, and 5 on the
same graph. (Hint: compute the fourier series.)