.

You now have a quadratic equation in .

So let , so that you can see the Quadratic:

.

So or .

This means or .

Case 1:

, where is an integer.

, where is an integer.

Case 2:

Since sine is positive in the first and second quadrants:

.

So putting it together:

.

Upon substituting and , we find all the possible solutions in the domain :

.