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

*To*: mathgroup at smc.vnet.net*Subject*: [mg120479] Simplify[ArcTan[Tan[a] + Tan[b]]]*From*: rych <rychphd at gmail.com>*Date*: Mon, 25 Jul 2011 07:28:34 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

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