we have the equation

Simplify

Remember that
The function sine is equal to the function cosine when the angle x is 45 degrees (pi/4)
so
I quadrant ---------> pi/4
II quadrant ----> No solution (different signs)
III quadrant -------> pi+pi/4=5pi/4
IV quadrant ----> No solution (different signs)
therefore
The answer is
x=pi/4,5pi/4