Re: Question on ComplexExpand

*To*: mathgroup at smc.vnet.net*Subject*: [mg51137] Re: [mg51129] Question on ComplexExpand*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 6 Oct 2004 04:34:09 -0400 (EDT)*References*: <200410050837.EAA08439@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On 5 Oct 2004, at 17:37, Carlos Felippa wrote: > *This message was transferred with a trial version of CommuniGate(tm) > Pro* > This question is related to a previous post, and to a project in > stability of a G&C feedback system I am working on. > > Is there a way to get ComplexExpand to automatically convert Abs to > Sqrt, Arg to ArcTan, etc., as target functions? For example > > ComplexExpand[Abs[x+y*I]] gives Sqrt[x^2+y^2] > ComplexExpand[Arg[x+y*I]] gives ArcTan[y/x] > > (Note: ComplexExpand assumes all symbols are real by default.) > I wasnt able to find an option to do that in 4.2.1. Thanks. > ComplexExpand[Abs[x + y*I], TargetFunctions -> {Re, Im}] Sqrt[x^2 + y^2] ComplexExpand[Arg[x + y*I], TargetFunctions -> {Re, Im}] ArcTan[x, y] Andrzej Kozlowski Chiba, Japan http://www.akikoz.net/~andrzej/ http://www.mimuw.edu.pl/~akoz/

**References**:**Question on ComplexExpand***From:*carlos@colorado.edu (Carlos Felippa)