alt Hacker NewsI don’t think I ever used atanh, but I always love some floating-point nerdery. These other documents by the same team are fantastic resources: https://inria.hal.science/hal-04714173v2/document for complex values and https://members.loria.fr/PZimmermann/papers/accuracy.pdf for real values.
Lots of good stuff here: https://members.loria.fr/PZimmermann/papers/ .
Tanh, and therefore atanh, are wonderful.
It's linear for small x, and exponential for large. Lots of applications of this:
Compressing data
Mapping (zoomed in near by, zoned out from afar)
There's a whole class of electronics amps for this.