Answer Happy

(a) (4 marks) Determine whether or not the following signals are periodic. If a signal is periodic, specify its fundamental period. (i) (2 marks) x1(t) = [ejat +e-jat] cos(at). (ii) (2 marks) 22[n] = sin((7n) +1], n € Z. (b) (12 marks) Below show six system equations, where the input and output are given by e(t) and y(t), respectively. For each of the equations, determine if the corresponding system is time-invariant or time-varying, and explain your reasons. (i) (2 marks) y(t) = tr(t) = = (ii) (2 marks) y(t) = c(t – 2) (iii) (2 marks) y(t) = $_$ 2()dt (iv) (2 marks) y(t) = x(-t) (v) (2 marks) y(t) = (dame))2 = dt2