AMC 12 2017b Problem 7

The functions $\sin(x)$ and $\cos(x)$ are periodic with least period $2\pi$. What is the least period of the function $\cos(\sin(x))$?

It's not periodic.

\textbf{(A)}\ \frac{\pi}{2} \textbf{(B)}\ \pi \textbf{(C)}\ 2\pi \textbf{(D)}\ 4\pi \textbf{(E)}