Platform and version requirements: JVM (1.2), JS (1.2), Native (1.2)

fun acos(x: Double): Double

fun acos(x: Float): Float

Computes the arc cosine of the value x; the returned value is an angle in the range from 0.0 to PI radians.

Special cases: - acos(x) is NaN, when abs(x) > 1 or x is NaN