Consider the following signals, sketch each one of them and comment on the periodic nature:
(a) x(t) = A cos(2πf_{0}t + θ), where A, f_{0}, and θ are the amplitude, frequency, and phase of the signal.
(b) x(t) = e^{j(2πf0t+θ)} , A> 0.
(c) Unit step signal u_{-1}(t) defined by u_{-1}(t) =
(d) Discrete-time signal x[n] = A cos(2πf_{0}n + θ), where n is an integer.