NAME

atanh, atanhf, atanhl - inverse hyperbolic tangent function

SYNOPSIS

#include <math.h>

double atanh(double x);

float atanhf(float x);

long double atanhl(long double x);

Link with -lm.

DESCRIPTION

The atanh() function calculates the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x. If the absolute value of x is greater than 1.0, atanh() returns not-a-number (NaN) and errno is set.

ERRORS

EDOM

x is out of range.

CONFORMING TO

SVID 3, POSIX, 4.3BSD, ISO 9899. The float and long double variants are C99 requirements.

SEE ALSO

acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3)