Find all solutions of the given equation in the interval Í0, 2π)

cos x/2 − s i n x = 0

recall that 2 sin x/2 cos x/2, so the equation becomes

cos x/2 - 2 sin x/2 cos x/2 = 0
cos x/2 (1 - 2sin x/2) = 0

I think you can handle that, right?