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MathGroup Archive 1999

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Re: Finding real part (newbie question)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15825] Re: Finding real part (newbie question)
  • From: phbrf at t-online.de (Peter Breitfeld)
  • Date: Fri, 12 Feb 1999 18:39:46 -0500 (EST)
  • Organization: das ist ein breites Feld ...
  • References: <79e8lo$9du@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Gnalle <GNALLE at MMF.ruc.dk> schrieb:
> If a,b,c,d are real numbers. How do I use mathematica to find the real
> part of
> 
> 1/(a + I b + 1/(c + I d))
> 
> Yes I can calculate it by hand, but I would like to know how to use
> Mathematica.

Try this:

z=1/(a + I b + 1/(c + I d)

this gives the real-part:

In[1]=
z1=ComplexExpand[z,TargetFunctions->{Re,Im}]//.Complex[0,_]->0
//Simplify

Out[1]=
               c + a c^2 + a d^2
-------------------------------------------------- 
1 + 2 a c - 2 b d + a^2(c^2 + d^2) + b^2(c^2 + d^2)

The imaginary part is then z-z1.

es gruesst
      Peter
-- 
=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=--=
  Peter Breitfeld, Saulgau, Germany       (PGP public key: 08548045)


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