1.9 atanh, atanhf—inverse hyperbolic tangent

Synopsis

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

Description
atanh calculates the inverse hyperbolic tangent of x.

atanhf is identical, other than taking and returning float values.

Returns
atanh and atanhf return the calculated value.

If

x|

is greater than 1, the global errno is set to EDOM and the result is a NaN. A DOMAIN error is reported.

If

x|

is 1, the global errno is set to EDOM; and the result is infinity with the same sign as x. A SING error is reported.

Portability
Neither atanh nor atanhf are ANSI C.