Answer:
f(x) = cos 2x = 2 cos^2 x - 1
Step-by-step explanation:
Here, we want to rewrite the given function using the power reducing formula
f(x) = cos 2x
Recall;
cos 2x = cos(x + x)
= cos x • cos x - sin x• sin x
= cos^2 x - sin^2 x
But Sin^2 x = 1 - cos^2x
Thus;
Cos^2x - sin^2 x = cos^2 x - (1 - cos^2 x)
= cos^2 x + cos^2 x - 1 = 2 cos^2 x - 1
