What is the equation of a half sine wave?

Question

Basically, I am trying to generate a half sine wave using excel. The waveform that I am looking for is a wave which has a positive component from $0$ to $\pi$ and a zero component from $\pi$ to $2\pi$. Image attached for reference (red graph). I'm looking for the equation of said graph. Graph of half-rectified sine wave

Answer 1

How about $$ f(x) = \frac{1}{2}\left(\sin(x) + \left| \sin{x} \right| \right) $$