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2017-09-15
Aliases: acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosf(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3), acosl(3)

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Manual pages about using GNU/Linux for development

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Linux kernel and C library user-space interface documentation

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).
Interface Attribute Value
Thread safety MT-Safe

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.

COLOPHON

This page is part of release 5.00 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/.
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