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# acosh(3)

2017-09-15
Aliases: acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshf(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3), acoshl(3)

### manpages-dev

Manual pages about using GNU/Linux for development

### man-pages

Linux kernel and C library user-space interface documentation

## 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);

```
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

## 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 Thread safety MT-Safe

## CONFORMING TO

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