Answer
$y(t)=-6sin(\frac{\pi}{6}t)$
Work Step by Step
Model with equation $y=a\cdot sin(\omega t)$, based on the figure of the problem, we can find that
$a=-6, \frac{2\pi}{\omega}=12, \omega=\frac{\pi}{6}$, thus the equation becomes $y(t)=-6sin(\frac{\pi}{6}t)$
