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MathGroup Archive 1999

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Re: ComplexExpand (V4.0)

  • To: mathgroup at
  • Subject: [mg20396] Re: ComplexExpand (V4.0)
  • From: "Stephen P Luttrell" <luttrell at>
  • Date: Tue, 26 Oct 1999 00:32:51 -0400
  • Organization: Defence Evaluation and Research Agency
  • References: <7u7rm9$>
  • Sender: owner-wri-mathgroup at

Blimbaum Jerry DLPC <BlimbaumJE at> wrote in message
news:7u7rm9$p3h at
> Why does ComplexExpand[Re[1/(x + I y)]]   return
> x/Abs[x+ I y]^2
> rather then      x/(x^2+y^2)
> The Mathematica manual says that ComplexExpand assumes that the
> variables are real.

I have $Version = "4.0 for Microsoft Windows (April 21, 1999)"

This does what you want:

ComplexExpand[Re[1/(x + I y)], TargetFunctions -> {Re, Im}]

Stephen P Luttrell
Room EX21, Defence Evaluation and Research Agency
Malvern, Worcs, WR14 3PS, U.K.
luttrell at
01684-894046 (phone), 01684-894384 (fax)

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