ACOS logarithmic form

[Claudio L.]

(04-28-2016 06:42 PM)Ángel Martin Wrote:  It's commonly accepted to define as "principal" branch the solution with argument between -pi and pi. This is covered with good explanations in the 15C Special Functions Manual, I'm sure somebody here will be able to point at its URL...

I know it might seem trivial, but once you get into the subject in depth it's a mess.
Each transcendental function has its own weird branch cuts, not so trivial as you can see here.
EDIT: What you mentioned works for ln() and sqrt(), acos() is a different animal.