$f(x) = 3\sin(\frac{\pi}{2}(x - \frac{\pi}{2}))$

$f(x) = 3\sin(\frac{\pi}{2}(x - 2))$

$f(x) = 4\sin(\frac{\pi}{3}(x - \frac{\pi}{2}))$

$f(x) = 3\sin(4(x - \frac{\pi}{2}))$