Re: Simplification and Arg[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg66599] Re: Simplification and Arg[]*From*: "Jaccard Florian" <Florian.Jaccard at he-arc.ch>*Date*: Mon, 22 May 2006 18:14:30 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

hello! I must admit it is difficult to guess... ComplexExpand[Arg[a + b*I], TargetFunctions -> {Re, Im}] gives ArcTan[a, b] ComplexExpand[Arg[1 + I*x] + Arg[1 - I*x], TargetFunctions -> {Re, Im}] gives 0 Regards F.Jaccard ________________________________ De: Andrew Moylan [mailto:andrew.moylan at anu.edu.au] =C0: mathgroup at smc.vnet.net Objet : [heur] [mg66593] Simplification and Arg[] Should Mathematica be able to simplify the following expression? (It is easily seen to be zero under the given condition, x > 0.) FullSimplify[ Arg[1 + I * x] + Arg[1 - I * x], {x > 0} ] In particular, I would have expected the following to yield ArcTan[b / a], from which the above expression is easily reduced to zero: FullSimplify[ Arg[a + I b], {a > 0, b > 0} ] Any ideas? Cheers, Andrew P.S. Apologies if I have sent this twice; my original message seems not to have worked.