How do you find the amplitude and period of a function y = sin (4x)?

Amplitude = 1 and period = $\frac{\pi}{2}$.
The amplitude and period of y = a sin (bx + c ) are a and $\frac{2 \pi}{b}$.
This sine wave oscillates between the crests at y = 1 and the lowest points at $y = - 1$, periodically, with period $\frac{\pi}{2}$ for one full wave.