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

*To*: mathgroup at smc.vnet.net*Subject*: [mg120508] Re: Simplify[ArcTan[Tan[a] + Tan[b]]]*From*: Jay Bee <jiri.bocan at gmail.com>*Date*: Wed, 27 Jul 2011 06:10:42 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j0jk6s$ovj$1@smc.vnet.net>

Since tg(a) + tg(b) = sin(a+b)/[cos(a)*cos(b)] = tg(a+b)*[1-tg(a)*tg(b)] = [tg(a)*tg(b)]*[cotg(a) + cotg(b)] maybe Mathematica is right...