Rotate Three

The function $latex f(x)=50x$ passes through the dashed line segment at $latex 120^{\circ}$ exactly 3 times in the interval $latex 0 \leq x \leq 20$.  Find other functions that do this.  To be clear, the segment does not have to rotate all the way around 3 times.  It just has to cross over the dashed line 3 times.