Periodic Function

A function f(x) is said to be periodic if there exists T>) such that f(x+T)=f(x)for all x in the domain of definition of f(x)

Since


for all n Є Z ( n belongs to Z)

sin (2nπ +x) = sin x
cos (2nπ +x) = cos x
tan (nπ +x) = tan x

sin x, cos x,and tan x are peridic functions.