The trigonometric equation is .

Consider .

Apply half - angle formula : .

\ \

\ \

.

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 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 solution is in the interval .

Thus, the solutions are , , and in the interval . 

The solutions are , , and in the interval .