       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
>
>
>

==== [MESSAGE SEPARATOR] ====

```

• Prev by Date: Re: [Q] Programming & "Not Floating Point Number" Error