Question

Consider the signal cos(30t) sampled at s=40rad/s using a unit impulse train. The sampled signal is filtered with an ideal low pass filter with unity gain and cutoff frequency c=40rad/s. The resulting output is

Answer 1

The unit impulse train is also called the III or comb function. Sampling a signal ... overlap, so low pass filtering recovers original signal. Cutoff frequency of low pass filter should satisfy.