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Question on ComplexExpand

• To: mathgroup at smc.vnet.net
• Subject: [mg51129] Question on ComplexExpand
• From: carlos at colorado.edu (Carlos Felippa)
• Date: Tue, 5 Oct 2004 04:37:26 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

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.

• Follow-Ups:
  • Re: Question on ComplexExpand
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>