The Trigonometric equation is .

Double angle formula: .

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 .

The solution set is .

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 .

Therefore,  the solutions in the interval are .

Consider .

.

Solution is

and

.

For complete solution we need to combine above two solutions

Combine solutions is and .

Arrange in ascending order.

.

The solution for is .