Section (3) acosh

Section 3 Linux manual pages

Name

acosh, acoshf, acoshl — inverse hyperbolic cosine function

Synopsis

`#include <math.h>`
 ```double acosh(``` double x`)`;

 ```float acoshf(``` float x`)`;

 ```long double acoshl(``` long double x`)`;

Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
`acosh`():
`_ISOC99_SOURCE` || `_POSIX_C_SOURCE` >= 200112L || `_XOPEN_SOURCE` >= 500 || /* Since glibc 2.19:
*/ `_DEFAULT_SOURCE` || /* Glibc versions <= 2.19:
*/ `_BSD_SOURCE` || `_SVID_SOURCE`
`acoshf`(), `acoshl`():
`_ISOC99_SOURCE` || `_POSIX_C_SOURCE` >= 200112L || /* Since glibc 2.19:
*/ `_DEFAULT_SOURCE` || /* Glibc versions <= 2.19:
*/ `_BSD_SOURCE` || `_SVID_SOURCE`
Note Link with `−lm`.

DESCRIPTION

These functions calculate the inverse hyperbolic cosine of `x`; that is the value whose hyperbolic cosine is `x`.

RETURN VALUE

On success, these functions return the inverse hyperbolic cosine of `x`.

If `x` is a NaN, a NaN is returned.

If `x` is +1, +0 is returned.

If `x` is positive infinity, positive infinity is returned.

If `x` is less than 1, a domain error occurs, and the functions return a NaN.

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 less than 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 `acosh`(), `acoshf`(), `acoshl`() Thread safety MT-Safe

CONFORMING TO

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

The variant returning double also conforms to SVr4, 4.3BSD.

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/.