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)