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MathGroup Archive 1996

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Re: Complex numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5445] Re: Complex numbers
  • From: ianc (Ian Collier)
  • Date: Sat, 7 Dec 1996 00:26:21 -0500
  • Organization: Wolfram Research, Inc.
  • Sender: owner-wri-mathgroup at wolfram.com

In article <57tvhr$k0f at dragonfly.wolfram.com>, Wouter Dobbelaere
<Wouter.Dobbelaere at rug.ac.be> wrote:

> Hi,
> 
> Is there a way to calculate the real or imaginary part of a complex
> expression symbolically (assuming real numbers as parameters) like:
> 
> Re[x + I y] = x
> 
> The standard Re function doesn't seem to allow that. Maybe some
> extensions exist?
> 
> Regards,
> Wouter Dobbelaere

You can use Complex Expand to do what you want:

In[2]:=
    expr= Re[x + I y]

Out[2]=
    -Im[y]+Re[x]

In[4]:=
    ?ComplexExpand

"ComplexExpand[expr] expands expr assuming that all variables are real. 
ComplexExpand[expr, {x1, x2, ... }] expands expr assuming that variables 
matching any of the xi are complex."

In[3]:=
    ComplexExpand[expr]

Out[3]=
    x

I hope this helps.

--Ian

-----------------------------------------------------------
Ian Collier
Wolfram Research, Inc.
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tel:(217) 398-0700   fax:(217) 398-0747    ianc at wolfram.com
Wolfram Research Home Page:         http://www.wolfram.com/
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