Rotate Three

Rotate Three

The function $f(x)=50x$ passes through the dashed line segment at $120^{\circ}$ exactly 3 times in the interval $0 \leq x \leq 20$ . 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.

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