Re: Re: Re: symbolic complex expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg53781] Re: [mg53759] Re: Re: [mg53637] symbolic complex expressions*From*: Pratik Desai <pdesai1 at umbc.edu>*Date*: Thu, 27 Jan 2005 05:41:19 -0500 (EST)*References*: <200501260937.EAA00248@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Bob Hanlon wrote: >$Version > >5.1 for Mac OS X (October 25, 2004) > >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) > >There is no indication that ComplexExpand has changed from v4.2 to v5.1 > >Try starting with a fresh kernel. > > >Bob Hanlon > > > >>From: "Frank Deicke" <frankdeicke at gmx.de> To: mathgroup at smc.vnet.net >> >>Date: 2005/01/25 Tue AM 10:44:48 EST >>CC: mathgroup at smc.vnet.net >>Subject: [mg53781] [mg53759] Re: [mg53637] symbolic complex expressions >> >>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 >>>>Subject: [mg53781] [mg53759] [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 >> >> >> > > > Try this for the first part Clear[a,b] TagSet[a,Im[a],0] TagSet[b,Im[b],0] TagSet[a,Re[a],a] TagSet[b,Re[b],b] lamda=a+I*b ComplexExpand[Abs[lamda]] >>

**References**:**Re: Re: symbolic complex expressions***From:*Bob Hanlon <hanlonr@cox.net>