I'm trying to find the fourier series of,

f(t) = cos(4t) + sin(6t)

I know the period is pi and wo = 2.

The equation I have been using is

an = (2 / pi) * integral(0 to pi) [ cos(4t)*cos( wo*n*t)]

then I add this to the corresponding "an" of sin(6t). I keep getting zeros for all constants ao, an, and bn. My question is, what do I use for "wo?" Do I use 2 for all constants? Or do I use the particular wo for each term, e.g., 4 for cos(4t) and 6 for sin(6t). Are my limits of integration correct? I thought you went to 0 to T where T is the period.

Thanks