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Re: Simplifying Expressions containing SQRT
*To*: mathgroup at smc.vnet.net
*Subject*: [mg3162] Re: [mg3126] Simplifying Expressions containing SQRT
*From*: jpk at apex.mpe.FTA-Berlin.de (Jens-Peer Kuska)
*Date*: Fri, 9 Feb 1996 03:02:17 -0500
*Sender*: owner-wri-mathgroup at wolfram.com
> Hi everybody!
>
> Strange things do happen!
>
> Mathematica4s ability to simplify equitations containing square roots
> seems to be quite weak. Perhaps I just do not know enough about these
> things, but I did read the manual. An example:
>
> Sqrt [ R ( R - x ) ] Sqrt [ ( R - x ) x ] / ( R x - R^2 )
>
>
> equals Sqrt[ R / x ], but I can4t get Mathematica figure that out.
>
> I tried PowerExpand, Factor, Collect, Simplify and almost everything
> else in various orders. Nothing worked! What can I do?
>
> I do appreciate every helpful hint. Thank you very much.
>
>
> Eric von Lieres lieres at studm.hrz.uni-siegen.de
>
> ------------------------------------------------------------
Hi Eric,
Try
In[]:= test=Sqrt[R*(R-x)]*Sqrt[(R-x)*x]/(R*x-R^2)
Out[]=
Sqrt[R (R - x)] Sqrt[(R - x) x]
-------------------------------
2
-R + R x
In[]:= test //. {
Sqrt[a_]*Sqrt[b_] :>
Sqrt[a*b],
Sqrt[a_]/b_ :>
Sqrt[Simplify[a/b^2]]
}
Out[]=
x
Sqrt[-]
R
You see, it is not obvious that yields a simplification in general, but
here it works fine.
Hope that helps
Jens
> Eric von Lieres lieres at studm.hrz.uni-siegen.de
>
>
>
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