xref: /freebsd/lib/msun/man/atanh.3 (revision 3a8617a83f16ffc9db4f96e1f0f21af94078e6b1)

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.\"     from: @(#)atanh.3	5.2 (Berkeley) 5/6/91
.\"	$Id: atanh.3,v 1.4 1993/10/29 22:57:24 jtc Exp $
.\"
.Dd May 6, 1991
.Dt ATANH 3
.Os BSD 4.3
.Sh NAME
.Nm atanh
.Nd inverse hyperbolic tangent function
.Sh SYNOPSIS
.Fd #include <math.h>
.Ft double
.Fn atanh "double x"
.Sh DESCRIPTION
The
.Fn  atanh
function computes the inverse hyperbolic tangent
of the real
argument
.Ar x .
For a discussion of error due to roundoff, see
.Xr math 3 .
.Sh RETURN VALUES
The
.Fn atanh
function
returns the inverse hyperbolic tangent of
.Ar x
if successful.
On the
.Tn VAX
and
.Tn Tahoe ,
if the argument has absolute value
bigger than or equal to 1,
.Fn atanh
sets the global variable
.Va errno
to
.Er EDOM
and
a reserved operand fault is generated.
.Sh SEE ALSO
.Xr acosh 3 ,
.Xr asinh 3 ,
.Xr exp 3 ,
.Xr infnan 3 ,
.Xr math 3
.Sh HISTORY
The
.Fn atanh
function appeared in
.Bx 4.3 .