The trigonometric equation is .

Consider .

Apply double angle identity : .

Common out from the left hand sdie.

Apply zero product property.

and 

and

Conisder .

.

General solution of is , where is an integer.

General solution is , where is an integer.

Find the angle in the interval .

General solution is , where is an integer.

If , .

If , .

Thus, the solutions are and in the interval .

Consider .

.

General solution of is , where is an integer.

General solution is , where is an integer.

Find the angle in the interval .

General solution is , where is an integer.

If , .

If , .

Thus, the solutions is in the interval .

Thus, the solutions of are and in the interval .

The solutions of are and in the interval .