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MathGroup Archive 2005

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Re: Re: symbolic complex expressions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53759] Re: Re: [mg53637] symbolic complex expressions
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Wed, 26 Jan 2005 04:37:14 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

$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
> To: hanlonr at cox.net
> CC: mathgroup at smc.vnet.net
> Subject: [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
> > > To: mathgroup at smc.vnet.net
> > > Subject: [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
> 


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