# Quick hyperbolic query

1. Jun 9, 2005

### Gaz031

This isn't exactly homework but I thought it was too basic to justify putting this post in the general math section.
My question is: why is arcoshx defined as: arcoshx=ln[x+rt(x^2-1)] and not +-ln[x+rt(x^2-1)] ?
Is it simply to keep it as a one to one function? I know that to have an inverse a function should be one to one but why is it not allowed for an inverse function to be 1 to 2 mapping?

Last edited: Jun 9, 2005
2. Jun 9, 2005