a. Let x[n] and y[n] be periodic signals with fundamental periods N1 and N2, respectively.
Under what conditions is the sum x[n] + y[n] periodic? If it is periodic, what is the fundamental period of this signal?
b. Consider two signals
x(t) = cos(2?t/3) + 2 sin(16?t/3), y(t) = sin(?t).
Is z(t) = x(t)y(t) periodic? If so, determine the fundamental period. If not, why?