Kevin Davies added the comment: I'm not sure what the resolution is (the patch was 'inverse', Mark said he'd be happy to use 'area', and Raymond quoted 'arc'). I didn't know this would be a big deal, and I'm sorry that I caused trouble. But since one of the concerns was divergence, I thought I'd send some info on how the tools I've used describe it -- universally as 'inverse' in those that I found: - Mathematica: ArcCosh[z] "gives the inverse hyperbolic cosine [...]" (http://reference.wolfram.com/mathematica/ref/ArcCosh.html) - Modelica Standard Library: acosh "Inverse of cosh (area hyperbolic cosine)" (http://reference.wolfram.com/system-modeler/libraries/Modelica/Modelica_Math...) - Maple: arccosh, but unknown description (http://www.maplesoft.com/support/help/Maple/view.aspx?path=invtrig) - MATLAB: acosh " Inverse hyperbolic cosine" (http://www.mathworks.com/help/matlab/ref/acosh.html) - TI-89 calculator: cosh-1 "returns the inverse hyperbolic cosine [...]" (from manual) Respectfully, Kevin ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21902> _______________________________________