Part 1
Choose the signal $ x(t)=cos(t) $ which is periodic.
File:Ctsignal.jpg
300px
Sampling ever interger yields
File:Dtsignal.jpg
300px
This is $ x[n]=cos(n) $
but sampling at a frequency of $ \pi/4 $ yields
File:Dtsignal1.jpg
300px
This is $ x[n]=cos(\pi/4n) $
Part 2
This is $ x(t)=e^{-t}cos(20t) $ as the nonperiodic signal.
File:Ctsignal3.jpg
300px
