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MathGroup Archive 2006

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Re: ComplexityFunction affects set of transformations tried by Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71550] Re: ComplexityFunction affects set of transformations tried by Simplify
  • From: "Schochet" <schochet at netvision.net.il>
  • Date: Wed, 22 Nov 2006 05:22:30 -0500 (EST)
  • References: <200611202311.SAA18396@smc.vnet.net><ejuqdp$htk$1@smc.vnet.net>

On Nov 21, 2:11 pm, Andrzej Kozlowski <a... at mimuw.edu.pl> wrote:
> On 21 Nov 2006, at 08:11, Schochet wrote:
>
> > As part of a large computation, I wanted Mathematica to
> > simplify expressions of the form   Sqrt[c + d/k](c k + d)2,
> > where k is positive, to   (c k + d)^(5/2)/Sqrt[k]
>
>
> Rather unlikely, I would say. Consider that my Mathematica 5.1 gives:
>
> expr1 = Sqrt[c + d/k]*(d + c*k)*2;
> expr2 = (d + c*k)^(5/2)/Sqrt[k];
>
> Simplify[expr1 == expr2, k > 0]
>
> (d + c*k - 2)*Sqrt[d + c*k] == 0
>

> So, the way I see it there are two possibilities. One is, that there
> was something funny with the state of your Mathematica when you got
> those results. If not, then I am  pleased that I have not upgraded
> from version 5.1 to 5.2 ;-)
>
> Andrzej Kozlowski
> Tokyo, Japan

In the course of transferring expr1 from Mathematica to my mail program
(on a different computer),
the ^ before the final 2 got lost. So expr1 should be: expr1 = Sqrt[c +
d/k]*(d + c*k)^2
Can you try the calculation again in Mathematica 5.1? I ran it in a new
Mathematica 5.2 session,
so I don't think the state of the sessuion is an issue.

Steve


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