Answer
The amplitude of the function is 2 and period is $\pi $.
Work Step by Step
The given equation is in the form of $y=A\cos Bx$. Here, $A=-2\text{ and }B=2$
So, the amplitude is:
$\begin{align}
& \text{Amplitude=}\left| A \right| \\
& =\left| -2 \right| \\
& =2
\end{align}$
The period is:
$\begin{align}
& \text{Period = }\frac{2\pi }{B} \\
& =\frac{2\pi }{2} \\
& =\pi
\end{align}$
$\text{Phase shift=}\frac{C}{B}=0$
So, the quarter period is as follows:
$\text{Quarter-period}=\frac{\pi }{4}$
Now, add quarter periods starting from $x=0$ to generate x-values for the key points. The x-value for the first key point is as follows:
$x=\text{0}$
And the x-value for the second key point is:
$\begin{align}
& x=0+\frac{\pi }{4} \\
& =\frac{\pi }{4}
\end{align}$
And the x-value for the third key point is:
$\begin{align}
& x=\frac{\pi }{4}+\frac{\pi }{4} \\
& =\frac{\pi }{2}
\end{align}$
And the x-value for the fourth key point is:
$\begin{align}
& x=\frac{\pi }{2}+\frac{\pi }{4} \\
& =\frac{3\pi }{4}
\end{align}$
And the x-value for the fifth key point is:
$\begin{align}
& x=\frac{3\pi }{4}+\frac{\pi }{4} \\
& =\pi
\end{align}$
