redhat man page for acos

ACOS(3) 						     Linux Programmer's Manual							   ACOS(3)

NAME
       acos - arc cosine function

SYNOPSIS
       #include <math.h>

       double acos(double x);

DESCRIPTION
       The  acos()  function  calculates  the  arc cosine of x; that is the value whose cosine is x.  If x falls outside the range -1 to 1, acos()
       fails and errno is set.

RETURN VALUE
       The acos() function returns the arc cosine in radians and the value is mathematically defined to be between 0 and PI (inclusive).

ERRORS
       EDOM   x is out of range.

CONFORMING TO
       SVID 3, POSIX, BSD 4.3, ISO 9899

SEE ALSO
       asin(3), atan(3), atan2(3), cos(3), sin(3), tan(3)

								    1993-06-08								   ACOS(3)