Re: Simplify[ArcTan[Tan[a] + Tan[b]]]

*To*: mathgroup at smc.vnet.net*Subject*: [mg120495] Re: Simplify[ArcTan[Tan[a] + Tan[b]]]*From*: Gary Wardall <gwardall at gmail.com>*Date*: Tue, 26 Jul 2011 07:06:19 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j0jk6s$ovj$1@smc.vnet.net>

On Jul 25, 6:31 am, rych <rych... at gmail.com> wrote: > Can't Mathematica tell anything about ArcTan[Tan[a] + Tan[b]]? Maybe > there exists no useful identity for that? By useful I mean the > expression with functions of the "angles" a and b other than tangents. > Thanks > Igor Igor, I'm not quite sure what you want Mathematica to do with it. It's not like ArcTan and Tan are truly inverses. ArcTan[Tan[W]] my not be W while Tan[ArcTan[W]] is W. Personally I think ArcTan[Tan[a] + Tan[b]] is simplified enough. Of course there are many alternate and equal expressions to it that could be of some use. But, which one? Gary