Find the values of θ, where θ ≤θ ≤ 360deg , that satisfy the equation: cosθ = - sqrt3/2

Question

Find the values of θ, where θ ≤θ ≤ 360deg , that satisfy the equation:

cosθ = - sqrt3/2

Answer 1

cosine is negative in quadrants II and III

cosine(theta) is -sqrt(3)/2 when reference angle (angle relative to horizontal axis) is 30 degrees in QII and QIII.

That occurs when theta is 150 and 210 degrees.