Question

Write the trigonometric expression as an algebraic expression. 2 cos(2 arccos x)

Answer 1

use \(\cos(2\theta) =\cos^2(\theta) - \sin^2(\theta) = 2\cos^2(\theta) - 1\)

Answer 2

Then \[
2\cos(2\arccos(x)) = 2(2\cos^2(\arccos(x)) - 1)
\]

Answer 3

In this case \(\theta = \arccos(x)\)