Atanh is included by default in each file as part of the Math library.
The Atanh() function returns the hyperbolic arctangent of a given unitless number. The result is given in radians, but it can be converted to degrees using "to deg".
Atanh() also works with complex numbers.
Examples of hyperbolic trig arc functions
Acosh(0.75) = (0 + 0.723i) rad
Acosh(5) to deg = 131.3 deg
Atanh(3ft/5ft) = 0.693 rad
Asinh(-i + 2i) = (7.825 + 1.571 i) rad