atanh

atanh, atanhf, atanhl - inverse hyperbolic tangent function

#include <math.h>
 I double atanh(double  x );

I float atanhf(float  x );

I long double atanhl(long double  x );
 

Link with -lm.

The R 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, R atanh () returns not-a-number (NaN) and errno is set.

EDOM

SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double variants are C99 requirements.

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