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MathGroup Archive 2000

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Re: Arithmetic simplification

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26222] Re: Arithmetic simplification
  • From: "Paul Lutus" <nospam at nosite.com>
  • Date: Sun, 3 Dec 2000 18:05:54 -0500 (EST)
  • References: <90a7o4$e8t@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Adalbert Hanssen" <hanssen at zeiss.de> wrote in message
news:90a7o4$e8t at smc.vnet.net...
> Hi, MathGroup,
>
> why does Mathematica return this sample expression unchanged
> (it can easily be simplified to 0, as the second
> part is just the first half with 1/3 factored out)?
>
> o30/3+(dw2*o46)/(3*o55)+o55/(3*dw2) - (o30+(dw2*o46)/o55+o55/dw2)/3
>
> Of course, in this case Simplify, Expand or Together
> find, that this is 0. This is only a sniplet from
> a larger expression with a dozen of ohter variables,
> indeed, o33, o46 and o55 are themselves expressions
> involving several other variables.
>
> I tried to simplify the large expression by hand
> (i.e. factor out common factors from partial sums
> etc) and I used Mathematica to check, if I did it
> right. However, in several cases, Together,
> PowerExpand and Simlify took "forever" after
> I did simplifications of the above kind.
>
> Is there a way to first apply Together etc
> only to Arguments of Sqrt, Power etc,
> in particular first to those Sqrt, Power etc,
> which are nested most deeply and apply thm
> to the higher ones after that?

I'd like to be able to help you, but Mathematica 4.0's result is:

In[1]:=
Simplify[o30/3 + (dw2*o46)/(3*o55) +
    o55/(3*dw2) - (o30 + (dw2*o46)/o55 + o55/dw2)/3]

Out[1]=
0

I guess it helps to include the version of Mathematica you are using. :)

--
Paul Lutus
www.arachnoid.com





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