## Linux and UNIX Man Pages

Test Your Knowledge in Computers #558
Difficulty: Medium
The term bug was popularized by Grace Hopper in 1947 while working on a Mark II Computer at a US Navy research lab when a moth was stuck in the computer.
True or False?

# acosh(3) [debian man page]

```ACOSH(3)						     Linux Programmer's Manual							  ACOSH(3)

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():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
acoshf(), acoshl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

DESCRIPTION
The acosh() function calculates 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.

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

asinh(3), atanh(3), cacosh(3), cosh(3), sinh(3), tanh(3)

COLOPHON
This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
be found at http://www.kernel.org/doc/man-pages/.

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

## Check Out this Related Man Page

```ACOSH(3)						     Linux Programmer's Manual							  ACOSH(3)

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   |
+-----------------------------+---------------+---------+
|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.