List two possible angles for cos^-1(1/2)

Answer 1

cos^-1(1/2) = π/3, because cos(π/3) = 1/2 and 0 ≤ π/3 ≤ π or cos^-1(1/2) = 60°, because cos60° = 1/2

and 0°≤ 60° ≤ 180°

Answer 2

arccos 0.5

cos θ = 0.5θ

θ ∈ {60°, 360°}