Answer
$$\cos300^\circ=\cos^2150^\circ-\sin^2150^\circ$$
25 is matched with F.
Work Step by Step
$$\cos300^\circ$$
We rewrite $300^\circ$ as double the angle $150^\circ$. In detail,
$$\cos300^\circ=\cos(2\times150^\circ)$$
This fact points to the use of the double identity for cosine, which states
$$\cos(2A)=\cos^2A-\sin^2A$$
Therefore, for $A=150^\circ$:
$$\cos300^\circ=\cos^2150^\circ-\sin^2150^\circ$$
The equation indicates that 25 should be matched with F.
