Answer
amplitude: $\frac{1}{2}$
period: $\frac{4\pi}{3}$
Work Step by Step
If a function has form $y=A\cos(\omega x)$, then there $|A|$ stands for the amplitude.
First we identify $\omega$ and $A$ from the form of $y=A\cos{(\omega x)}$.
Hence, $A=\left|-\frac{1}{2}\right|=\frac{1}{2}$, $\omega=1.5.$
To get the period $T$ we can use the formula: $T=\frac{2\pi}{\omega}$ to obtain
$T=\dfrac{2\pi}{\frac{3}{2}}=\dfrac{4\pi}{3}$