Part 1
Choose the signal $ x(t)=cos(t) $ which is periodic.
File:Ctsignal.jpg
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Sampling ever interger yields
File:Dtsignal.jpg
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This is $ x[n]=cos(n) $
but sampling at a frequency of $ \pi/4 $ yields
File:Dtsignal1.jpg
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This is $ x[n]=cos(\pi/4n) $
Part 2
This is $ x(t)=e^{-t}cos(20t) $ as the nonperiodic signal.
File:Ctsignal1.jpg
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