Answer
True
Work Step by Step
We have a definition of periodic:
A function $y=f(x)$ is periodic if there exists a positive real number $a$ such that
$f(x)=f(x+a)$
for all values of x in the domain of the function.
$\sin x=\sin(\pi+x)$, $\tan2x=\tan(2x+\pi)$.
Hence, all six of the basic trigonometric functions are periodic.
