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# acosl

## man page of acosl

### acosl: arc cosine function

```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);

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.

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

COLOPHON
This  page  is  part of release 3.27 of the Linux man-pages project.  A
description of the project, and information about reporting  bugs,  can
be found at //www.kernel.org/doc/man-pages/.

2010-09-20                          ACOSL(3)
```