HP-UX Reference (11i v1 05/09) - 3 Library Functions A-M (vol 6)

atanh(3M) atanh(3M)

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

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.