ATANH (Primitive Spread Function) returns the inverse hyperbolic tangent of a number.

SYNTAX:

ATANH(value)

REMARKS:

The value argument is any real number between 1 and –1, excluding –1 and 1.
Note that atanh(tanh(value)) equals value. 

EXAMPLES:

ATANH(B5)
ATANH(0.55)=0.6183813136
ATANH(-0.2)=-0.2027325541