Answer
6
Work Step by Step
We first write the equation in the form $y=c+a \cos [b(x-d)]$. Therefore, $y=3-6\sin (2x+\frac{\pi}{2})$ becomes $y=3-6\sin [2(x+\frac{\pi}{4})]$.
Comparing the equation to its general form, we find that $a=-6$.
We know that the amplitude is equal to $|a|$. Therefore,
amplitude=$|a|=|-6|=6$.
