Solve the equation sin2θ - cos2θ = - 1/2 for 0°≤ θ ≤ 360°

Question

Sole the equation sin²θ - cos²θ = - ½ for 0°≤ θ ≤ 360°

Answer 1

sin²θ − cos²θ = − 1
                            2
but sin²θ + cos²θ = 1
1 − 2cos²θ = −0.5
2cos²θ = 1.5
cos θ= ±0.8666
θ = 30 & 330 or 150 & 210