The trigonometric equation is .

Consider .

Factorize the above equation.

Apply zero product property.

and . 

Consider .

.

The general solution of is , where is an integer.

Divide each side by 2.

.

Consider .

The general solution of is , where is an integer.

Divide each side by 3.

.

Thus, the solutions are and , where is an integer.

The solutions are and , where is an integer.