◄Description► ◄Example► ◄Up► ◄Contents► ◄Index► ◄Back► ─────Run-Time Library─────────────────────────────────────────────────────── Include: <math.h> <errno.h> Required only for definition of errno constants Syntax: double acos( double x ); double asin( double x ); double atan( double x ); double atan2( double y, double x ); Returns: (acos) the arccosine result, or 0 if x is greater than 1 or less than -1. (asin) the arcsine result, or 0 if x is greater than 1 or less than -1. (atan) the arctangent result. (atan2) the arctangent result, or 0 if both arguments are 0. errno: EDOM See also: cos, sin, tan, _matherr -♦-