A certain band-limited periodic current has only three frequencies in its Fourier series representation: dc, 50 Hz,

Question:

A certain band-limited periodic current has only three frequencies in its Fourier series representation: dc, 50 Hz, and 100 Hz. The current may be represented as
I(t) = 4 + 6 sin 100πt + 8 cos100πt
-3 sin 200πt - 4 cos 200πt A
(a) Express i(t) in amplitude-phase form.
(b) If i(t) flows through a 2- Ω resistor, how many watts of average power will be dissipated?