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



NAME
       acos, acosf, acosl - arc cosine function

SYNOPSIS
       #include <math.h>

       double acos(double x);
       float acosf(float x);
       long double acosl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       acosf(), acosl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       The acos() function calculates the arc cosine of x; that is the value whose cosine is x.

RETURN VALUE
       On success, these functions return the arc cosine of x in radians; the return value is  in
       the range [0, pi].

       If x is a NaN, a NaN is returned.

       If x is +1, +0 is returned.

       If  x  is  positive  infinity  or  negative  infinity, a domain error occurs, and a NaN is
       returned.

       If x is outside the range [-1, 1], a domain error occurs, and a NaN is returned.

ERRORS
       See math_error(7) for information on how to determine whether an error has  occurred  when
       calling these functions.

       The following errors can occur:

       Domain error: x is outside the range [-1, 1]
              errno is set to EDOM.  An invalid floating-point exception (FE_INVALID) is raised.

CONFORMING TO
       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4, 4.3BSD, C89.

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

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



                                            2010-09-20                                    ACOS(3)