Solve the given equation. (Enter your answers as a comma-separated list. Let k be any integer. Round terms to three decimal places where appropriate. If there is no solution, enter NO SOLUTION.)

Question

2 cos2 θ − cos θ − 1 = 0

Answer 1

what's the problem. You know how to solve quadratics:

Let x = cosθ

2x^2 - x - 1 = 0
(2x+1)(x-1) = 0

x = -1/2 or 1
So,
cosθ = -1/2 or 1
. . .