Arc hyperbolic tangent

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double __far atanh(double x); (C99)

[Return value]

Returns the arc hyperbolic tangent of x.

If x is not inside the range [-1, +1], returns a Not-a-Number (NaN) and sets macro EDOM to global variable errno.

If x is -1, returns -HUGE_VAL and sets macro ERANGE to global variable errno.

If x is 1, returns HUGE_VAL and sets macro ERANGE to global variable errno.

[Description]

This function calculates the arc hyperbolic tangent of x. Specify the angle in radian.