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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 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2010-09-20                           ACOS(3)