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