precal
posted by stellar .
Solve the given equation. (Enter your answers as a commaseparated list. Let k be any integer. Round terms to three decimal places where appropriate. If there is no solution, enter NO SOLUTION.)
2 cos2 θ − cos θ − 1 = 0

what's the problem. You know how to solve quadratics:
Let x = cosθ
2x^2  x  1 = 0
(2x+1)(x1) = 0
x = 1/2 or 1
So,
cosθ = 1/2 or 1
. . .