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Arithmetic simplification

• To: mathgroup at smc.vnet.net
• Subject: [mg26210] Arithmetic simplification
• From: Adalbert Hanssen <hanssen at Zeiss.de>
• Date: Sat, 2 Dec 2000 02:10:38 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

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? 

kind regards

Dipl.-Math. Adalbert Hanszen