Fourier series:
Input CT signal: x(t) = 3cost+sin2t
=$ 3*\frac{e^jt+e^-jt}{2}+\frac{e^j2t-e^-j2t}{2}\, $ =$ 3/2e^jt}-3/2e^{-jt}+1/2e^{j2t}-1/2e^{-j2t} $
