The Trigonometric equation is .

Substitute the double angle formula

       \ \

                 \ \

    \ \

Since .

          \ \

           \ \ Apply zero rule property. \ \

and  \ \

First part .

The general solution of is , where is any integer. \ \

For ,

For , .

For , .

Therefore, the solutions in the interval are .

Second part

Apply zero rule property. \ \

and

and 

The general solution of is , where is any integer.

solution is

Substitute in , hence

Substitute in , hence

Substitute in , hence \ \

hence,

Therefore,  the solutions in the interval are .

Consider .

The solution set is .

Therefore, the solution is

and

For complete solution we need to combine above two solutions

Combine solutions is

Arrange in ascending order

The solution set for is .