hard and im lost

Question

Find all solutions of the given equation. (Enter your answers as a comma-separated list. Let k be any integer. Round terms to two decimal places where appropriate.)

4 cos² θ − 1 = 0

θ =

 

rad

Answer 1

Step 1:

The trigonometric equation is .

Let .

Difference of squares formula: .

Substitute in the factors.

General solution :

If , then , where is an integer.

General solution :

If , then , where is an integer.

Solution :

The general solution is .