# What is the period and amplitude for y = 1/2sin (x/3 - pi)?

The amplitude is represented by the number that multiplies the $\sin$, i.e., $\frac{1}{2}$; so your sine oscillates between $+ \frac{1}{2}$ and $- \frac{1}{2}$.
The period is given by the number that multiplies $x$ in the argument of sine, i.e., $\frac{1}{3}$, as:
$p e r i o d = \frac{2 \pi}{\frac{1}{3}} = 6 \pi$