Periodic and Non-Periodic Functions
Periodic Functions
A continuous time signal is periodic if there exists a value $ T $ such that $ x(t + T) = x(t) $.
A discrete time signal is periodic if there exists a value $ N $ such that $ X[n + N] = X[n] $.
As you can see in the graph, at time $ t = 0 $, $ x(t) = 0 $. This occurs again at $ t = 4/3\pi $, and again at $ -4/3\pi $.
