The trigonometric equation is .

Substitute the double angle formula .

Apply zero product rule

and

and \ \

We need to solve above two equations separately for solution

First part

The general solution of is , where is any integer.

.

For , .

For , .

For , .

Therefore, the solutions in the interval are .

Second part \ \

The general solution of is , where is any integer.

solution is

Substitute in , hence

Substitute in , hence

Substitute in , hence \ \

Therefore,

Therefore,  the solutions in the interval are .

For complete solution we need to combine above two solutions

combine solutions is

Arrange in ascending order

The solution for is .