 Solution

The function is even and continuous, with period $2\pi$. On $0<x<\pi$ it is $\sin 2x$, so it rises from zero to one at $\pi /4$, crosses zero at $\pi /2$, reaches minus one at $3\pi /4$, and returns to zero at $\pi$. Reflect this curve about the vertical axis and repeat periodically. The joins at integer multiples of $\pi$ have corners, but no jumps.