ACOS
Section: Linux Programmer's Manual (3)
Updated: 20170915
Page Index
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 floatingpoint exception
(FE_INVALID)
is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
Interface  Attribute  Value

acos(),
acosf(),
acosl()
 Thread safety  MTSafe

CONFORMING TO
C99, POSIX.12001, POSIX.12008.
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 5.02 of the Linux
manpages
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/manpages/.