NAME
atanh() — inverse hyperbolic tangent function
SYNOPSIS
#include <math.h>
double atanh(double x);
DESCRIPTION
The
atanh()
function computes the inverse hyperbolic tangent of its argument.
The ISO/ANSI C committee has approved the
atanh()
function for inclusion in the C9X draft standard.
To use this function, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options. Make sure your program includes
<math.h>.
Link in the math library by specifying
-lm
on the compiler or linker command line.
RETURN VALUE
If
x
is NaN,
atanh()
returns NaN.
If
|x|
> 1.0,
atanh()
returns NaN and sets
errno
to [EDOM].
If
|x|
= 1.0,
atanh()
returns
±HUGE_VAL
(according to the sign of
x)
and sets
errno
to
[ERANGE].
ERRORS
If
atanh()
fails,
errno
is set to one of the following values.
- [EDOM]
x
has an absolute value greater than 1.0.
- [ERANGE]
x
has an absolute value equal to 1.0.
STANDARDS CONFORMANCE
atanh(): SVID3, XPG4.2
