@c ----------------------------------------------------------------------
@node atanh, math
@subheading Syntax

@example
#include <math.h>

double atanh(double x);
@end example

@subheading Description

This function computes the inverse hyperbolic tangent of @var{x}.

@subheading Return Value

The inverse hyperbolic tangent of @var{x}.  If the the value of
@var{x} is plus or minus 1, the return value is an @code{Inf} with the
same sign as the argument @var{x}, and @code{errno} is set to
@code{ERANGE}.  If the absolute value of @var{x} is greater than 1, the
return value is @code{NaN} and @code{errno} is set to @code{EDOM}.

@subheading Portability

@portability !ansi, !posix