acos
Syntax:
#include <cmath> double acos( double arg );
The acos() function returns the arc cosine of arg, which will be in the range [0, pi]. arg should be between -1 and 1. If arg is outside this range, acos() returns NAN and raises a floating-point exception.
Related Topics: asin, atan, atan2, cos, cosh, sin, sinh, tan, tanh