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MathGroup Archive 2005

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Problem with D and Abs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60970] Problem with D and Abs
  • From: Daniele Lupo <danwolf80_no_spam_ at libero.it>
  • Date: Wed, 5 Oct 2005 02:28:21 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi to all.

I've a problem with this expression:

\!\(Abs[\(Conjugate[s11]\ g\_s\)\/\(1 + Abs[s11]\^2\ \((\(-1\) + g\_s)\)\)
- \
Ã\_0\/\(1 + N\_i\)] - \@\(N\_i\ \((1 - Abs[Ã\_0]\^2 + N\_i)\)\)\/\(1 +
N\_i\)\
\)


I want to have derivative in gs. If I use D, I obtain a strange result,
that invoke Abs'[...], that's not correct, naturally.

I've tried to use PiecewiseExpand, but I've a problem. In this expression,
\!\(g\_s\) and \!\(N\_i\) are real, while \!\(Ã\_0\) and s11 are complexes.
I don't know how to create an expansion that consider some symbol as real,
and some other as complex.

How can I do it?

Thanks for your answers.

Daniele

PS I'm using version 5.1, WinXP


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