Solve the equation for θ if 0° ≤ θ < 360°. (Enter your answers as a comma-separated list.) sin 2θ + cos θ = 0

Answer 1

Given: sin 2θ + cosθ = 0

2sinθcosθ + cosθ =0

cosθ(2sinθ + 1) = 0

==> cosθ = 0 or 2sinθ + 1 = 0

cosθ = 0 or sinθ = -1/2

∴ θ = 90⁰ or 270⁰ or θ = 210⁰ or 330⁰