Trigonometry Examples

$\cos (3 x) = 4 \cos^{3} (x) - 3 \cos (x)$

Step 1

Start on the right side.

$4 \cos^{3} (x) - 3 \cos (x)$

Step 2

Apply the cosine triple-angle identity.

$\cos (3 x)$

Step 3

Because the two sides have been shown to be equivalent, the equation is an identity.

$\cos (3 x) = 4 \cos^{3} (x) - 3 \cos (x)$ is an identity