How do you simplify sin2x=cosx

          sin(2x) = cos(x)
2sin(x)cos(x) = cos(x)  Expand sin(2x).
     2cos(x)      2cos(x) Divide 2cos(x) on each side.
            sin(x) = ¹/₂
    sin⁻¹[sin(x)] = sin⁻¹(¹/₂)   Use sin⁻¹(x) on each side.
                   x = 30, 150  Find the answer.

21/2 or 5/2