- `Y = atanh (X)`

Compute the inverse hyperbolic tangent for each element of `X`.

This is defined as

> > `%atanh(z) = 1/2*ln((1+z)/(1-z))%`

See also: `tanh`.

### References

- https://www.mathworks.com/help/matlab/ref/atanh.html
- https://octave.sourceforge.io/octave/function/atanh.html
- https://mathworld.wolfram.com/InverseHyperbolicFunctions.html
- https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions