NAME
atanh, atanhf, atanhl - inverse hyperbolic tangent function
SYNOPSIS
#include <math.h>
double atanh(double x);
float atanhf(float x);
long double atanhl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
atanh(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_ISOC99_SOURCE; or cc -std=c99
atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
|| _ISOC99_SOURCE; or cc -std=c99
DESCRIPTION
The atanh() function calculates 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 floating-point exception
(FE_INVALID) is raised.
Pole error: x is +1 or -1
errno is set to ERANGE (but see BUGS). A divide-by-zero
floating-point exception (FE_DIVBYZERO) is raised.
CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4,
4.3BSD, C89.
BUGS
For a pole error, errno is set to EDOM; POSIX.1 says it should be set
to ERANGE.
SEE ALSO
acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3)
COLOPHON
This page is part of release 3.24 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/.
2008-08-05