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. 

To use this function, 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. 

SEE ALSO

tanh(3M), asinh(3M), acosh(3M), isnan(3M). 

STANDARDS CONFORMANCE

atanh(): SVID3, XPG4.2

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996