[ThinBold]

Despite all the good contents, calling the inverse function of hyperbolic tangent "arctanh" just makes no sense.

[TheFattestNinja]

Isn't that the normal "math" name though? tan <-> arctan, tanh <-> arctanh ? What would you have called it? harctan?

[ThinBold]

For the hyperbolic version area is the correct counterpart of arc-length. See the wikipedia for a picture. So only "ar-" and "a-" make sense. Blindly using "arc-" is like saying non-invertible matrices are "vertible" because "in-" negates the meaning of a word.

[optimalsolver]

Isn't that how it's done in NumPy?

[ThinBold]

It probably inherits the name from other languages that get it wrong.