# How do you determine the amplitude and period of the function y=3cos((pix)/2)?

You can "read" these information from the numbers in your function, i.e, $3$ (multiplying $\cos$) and $\frac{\pi}{2}$ (multiplying $x$):
Amplitude is $3$ meaning that your function oscillates between $+ 3 \mathmr{and} - 3$;
Period is given using $\frac{\pi}{2}$ in the form of: $\left(p e r i o d\right) = \frac{2 \pi}{\textcolor{red}{\frac{\pi}{2}}} = 4$.