Consider a causal continuous-time LTI system whose input x(t) and output y(t) are related by the following differential equation:
dy(t)/dt + 4y(t) = x(t).
Find the Fourier series representation of the output y(t) for each of the following inputs:
a) x(t) = cos2πt
b) x(t) = sin 4πt + cos(6πt + π/4)