Answer
$y=3sin(4x-8)$.
Work Step by Step
1. Write a general form of the equation $y=A\ sin(\omega x-\phi)$.
2. From the given conditions, we have $A=3$, $\frac{2\pi}{\omega}=\frac{\pi}{2}$ or $\omega=4$, and $\frac{\phi}{\omega}=2$ or $\phi=8$.
3. Thus we have $y=3sin(4x-8)$.
