Answer
Amplitude=3
Period$=\pi$ sec
Frequency$=\frac{1}{\pi}$ cycles per second
Work Step by Step
We first need to compare $s(t)=3\cos2 t$ with the standard form of the equation $s(t)=a \cos wt$ where $a$ represents the amplitude and $w$ represents the angular speed.
Comparing the two equations, we find that $a=3$. This means that the amplitude is 3 inches. By comparison, we also find that $w=2$. $w$ can be used to find the period through the formula:
Period$=\frac{2\pi}{w}$
Period$=\frac{2\pi}{2}$
Period$=\pi$ sec
Since frequency is the reciprocal of period,
Frequency$=\frac{1}{\pi}$ cycles per second