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():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       These  functions calculate 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.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       allbox; lbw24 lb  lb  l  l  l.   Interface Attribute Value  T{  acos(),
       acosf(), acosl() T}   Thread safety  MT-Safe

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

       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 4.16 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
       https://www.kernel.org/doc/man-pages/.



                                  2017-09-15                           ACOS(3)