Manual Reference Pages - ACOS (3)
NAME
acos, acosf, acosl - arc cosine function
CONTENTS
Synopsis
Description
Errors
Colophon
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
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man-pages project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages /.

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