Re: Simplifying with positive constants

• To: mathgroup at smc.vnet.net
• Subject: [mg26081] Re: [mg26062] Simplifying with positive constants
• From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
• Date: Tue, 28 Nov 2000 01:55:28 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```on 00.11.22 3:55 PM, djago at my-deja.com at djago at my-deja.com wrote:

> I'm trying to calculate some results and when I evaluate them I get:
> 1/2(r*a-a*d-Sqrt[4*r*a^2*d+(-r*a+a*d)^2]
>
> I know that this is a complicated way of saying:
> r*a
>
> but Mathematica (3.0) doesn't seems to get the idea...
>
> I've tried with FullSimplify and so on... but Mathematica won't let a
> go out of the Sqrt function. Maybe If I could tell Mathematica that a,
> r and d are real and positive values...
>
> Can somebody give me a hint of how to do this???
>
> Thx!
>
>
> Sent via Deja.com http://www.deja.com/
>
>

This sort of thing is much easier to do in 4.0. Still, 3.0 can also manage

In[13]:=
1/2(r*a - a*d - Sqrt[4*r*a^2*d + (-r*a + a*d)^2]) // Simplify //
PowerExpand // Simplify

Out[13]=
-a d
--
Andrzej Kozlowski
Toyama International University
JAPAN

http://platon.c.u-tokyo.ac.jp/andrzej/
http://sigma.tuins.ac.jp/

```

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