Question

3cos^2 x-2 cos x-2=0

Answer 1

if you let \(y=\cos x\) then \[
3y^2-2y-2=0
\]You can solve for \(y\), and it should give two solutions.

Suppose they are \(y_1\) and \(y_2\).
Then you would use \(
y_1 = \cos(x)\) and \(
y_2 = \cos(x)
\) to get solutions for \(x\).