cos(q) + sinČ(q) = 0, 0 ≦ q < 360°
cos(2q) + sin2(q) = 0
We use the identity
1 - 2sin2 + sin2(q) = 0
1 - sin2(q) = 0
1 = sin2(q)
±1 = sin(q)
90° and 270° = q
Edwin