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A signal 
is sampled at 
and then passed through an ideal low pass filter having cut-off frequency of 
. The maximum frequency present in the filtered signal in 
is __________ (Round off to the nearest integer).
X(t) = 2 cos (180 πt) cos (60πt)
=cos (240 πt) + cos (120 πt)
So, spectrum of x(t) contains impulses at following frequencies: -120, 120, -60, 60
Due to sampling spectrum shifts by nfs
fs = sampling frequency = 200 Hz
n = 0 components: - 60, -120, 80, 120
n = 1 components: 140, 80, 260, 320
n = 2 components: 340, 280, 460, 520
∴ the sampled signal is passed through a LPF with cut off frequency = 100 Hz highest frequency passing through filters = 80 Hz