MathGroup Archive: July 2005 [00331]

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refining expression in terms of real numbers

To: mathgroup at smc.vnet.net
Subject: [mg58735] refining expression in terms of real numbers
From: "Mukhtar Bekkali" <mbekkali at gmail.com>
Date: Sat, 16 Jul 2005 01:03:43 -0400 (EDT)
Sender: owner-wri-mathgroup at wolfram.com

My expression is real for all values of gamma between half and one (I
plotted it just to be sure), yet the general solution that Mathametica
generates may imply that I have an unreal solution, an impression that
I would like to avoid. Is there a way to make Mathematica refine
solutions in terms of real numbers. Here is the input:

\!\(expr := Refine[Root[\(-160\) + 783\ Î³ + 54\
            Î³\^2 - 1059\ #1 - 540\ Î³\ #1 + 504\ #1\^2 + 80\ #1\^3 &,
2] //
                 ToRadicals, 1\/2 < Î³ < 1] //
Simplify\[IndentingNewLine]
  expr\[IndentingNewLine]
  \(Plot[expr, {Î³, 1\/2, 1}];\)\)

Thanks, Mukhtar Bekkali

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