Answer
Write $P$ in terms of $\sin(2\pi t)$: $$P=16k-16k\sin^2(2\pi t)$$
Work Step by Step
From part a), we have the expression of $P$ $$P=16k\cos^2(2\pi t)$$
From Pythagorean Identity, we have $$\cos^2\theta=1-\sin^2\theta$$
Therefore, similarly in $P$,
$$P=16k[1-\sin^2(2\pi t)]$$
$$P=16k-16k\sin^2(2\pi t)$$
