Periodic and Non-Periodic Functions
Periodic
In CT the cosine function cos(t) is a periodic function with fundamental period T = 2π. This comes from the definition of periodic systems. A function x(t) is periodic if there exists some T > 0 for which x(t + T) = x(t). In our case x(t) = cos(t) and T = 2π * n where n is an integer.
Non-Periodic
In CT let x(t)=e^[1+j2)t]=(e^t)×[cos(2t)+ jsin(2t)] is a non-periodic signal because there is no T for which x(t+T)= x(t). In this case the signals amplitude goes to ∞ as t goes to ∞.
