atanh (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting ...
NAME
atanh, atanhf, atanhl  inverse hyperbolic tangent functionSYNOPSIS
#include <math.h> double atanh(double x);Link with lm.
float atanhf(float x);
long double atanhl(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
atanh():

_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 500 
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
atanhf(), atanhl():

_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
DESCRIPTION
These functions calculate the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x.RETURN VALUE
On success, these functions return the inverse hyperbolic tangent of x.If x is a NaN, a NaN is returned.
If x is +0 (0), +0 (0) is returned.
If x is +1 or 1, a pole error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the mathematically correct sign.
If the absolute value of x is greater than 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 less than 1 or greater than +1
 errno is set to EDOM. An invalid floatingpoint exception (FE_INVALID) is raised.
 Pole error: x is +1 or 1
 errno is set to ERANGE (but see BUGS). A dividebyzero floatingpoint exception (FE_DIVBYZERO) is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).Interface  Attribute  Value 
atanh(), atanhf(), atanhl()  Thread safety  MTSafe 
CONFORMING TO
C99, POSIX.12001, POSIX.12008.The variant returning double also conforms to SVr4, 4.3BSD, C89.