do know how to work this hard one

Question

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.)

2 cos² θ − 5 cos θ + 2 = 0

θ =

 

Answer 1

The trigonometric equation is .

Let .

Substitute in the factors.

General solution :

Since , it has no real solutions.

General solution :

If , then , where is an integer.

.

The general solution is .