Part 1
The function was chosen at random from HW1: HW1.4 Hang Zhang - Periodic vs Non-period Functions_ECE301Fall2008mboutin
$ \,x(t)=2cos(2\pi t)\, $
Periodic Signal in DT:
If sampled at $ period=0.1 $, the function
$ \,y[n]=x[\frac{n}{10}]=2cos(\frac{2\pi n}{10})\, $
would be periodic, since
$ \,y[n]=y[n+10N], \forall N\in Z\, $
TODO: Add MATLAB plot of the DT function