Find the angle whose cosine equals a given value, with principal value in degrees or radians.
The inverse cosine (arccos) returns the angle whose cosine equals x. The principal value is in [0°, 180°] or [0, π]. The domain is [−1, 1].
Inverse cosine
θ = arccos(x), where −1 ≤ x ≤ 1
arccos(0.5) = 60°, because cos(60°) = 0.5.
arccos(−1) = 180°, the largest value in the principal range.