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MathGroup Archive 2005

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Re: symbolic complex expressions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53746] Re: [mg53637] symbolic complex expressions
  • From: "Frank Deicke" <frankdeicke at gmx.de>
  • Date: Wed, 26 Jan 2005 04:36:23 -0500 (EST)
  • References: <20050122023259.DVJU20686.lakermmtao07.cox.net@smtp.east.cox.net>
  • Sender: owner-wri-mathgroup at wolfram.com

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: [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
> > 
> > 
> 

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