Re: Re: symbolic complex expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg53774] Re: [mg53746] Re: [mg53637] symbolic complex expressions*From*: "David Park" <djmp at earthlink.net>*Date*: Thu, 27 Jan 2005 05:41:09 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Frank, Version 5 ComplexExpand seems to work better than Version 4.2. In 4.2 you have to use... ComplexExpand[Abs[x + I*y], TargetFunctions -> {Re, Im}] Sqrt[x^2 + y^2] ComplexExpand[x/(x + I*y), TargetFunctions -> {Re, Im}] x^2/(x^2 + y^2) - (I*x*y)/(x^2 + y^2) In Version 5 you can leave out the TargetFunctions option. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Frank Deicke [mailto:frankdeicke at gmx.de] To: mathgroup at smc.vnet.net Hi Bob, I try this but it does not realy work fine. I use mathematica version 4.2. Is there anything else like including a special package? In: ComplexExpand[Abs[x + I*y]] Out: Abs[x + I y] ??? or In: ComplexExpand[x/(x+I*y)] Out: x^2/Abs[x + I y]^2 - I x y/Abs[x + I y]^2 ??? Why you get another output? Thanks, Frank > ComplexExpand[Abs[x+I*y]] > > Sqrt[x^2 + y^2] > > ComplexExpand[x/(x+I*y)] > > x^2/(x^2 + y^2) - (I*x*y)/(x^2 + y^2) > > > Bob Hanlon > > > > > From: frankdeicke at gmx.de (Frank) To: mathgroup at smc.vnet.net > > Date: 2005/01/21 Fri AM 06:35:44 EST > > To: mathgroup at smc.vnet.net > > Subject: [mg53774] [mg53746] [mg53637] symbolic complex expressions > > > > Hi, > > > > I've 2 question with mathematica using symbolic complex expressions. > > > > - Is there a possibility to make from i.e. |x + I y| -> sprt(x^2+y^2) > > if x and y are Real. Abs[] doesn't work? > > > > > > - You've a fraction like this x/(x + I y) and you want to eliminate > > the complex expression in the denominator. > > i.e. doing something like this: x/(x + Iy)*(x - I y)/(x - I y) -> (x^2 > > - I x y)/(x^2+y^2) > > > > How do you do this with mathematica? > > > > Thanks, > > > > Frank > > > > > -- GMX im TV ... Die Gedanken sind frei ... Schon gesehen? Jetzt Spot online ansehen: http://www.gmx.net/de/go/tv-spot