Re: Re: Simplifying with positive constants

• To: mathgroup at smc.vnet.net
• Subject: [mg26109] Re: Re: [mg26062] Simplifying with positive constants
• From: Fernando Suarez Ornani <djago at usa.net>
• Date: Tue, 28 Nov 2000 01:55:56 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Is your Mathematica Version 3? I get:

In[8]:= Simplify[1/2(r*a - a*d - Sqrt[4*r*a^2*d + (-r*a + a*d)^2]),
a > 0 && r > 0 && d > 0]

Simplify::nonopt : Options expected (instead of (a > 0 && r > 0 && d > 0)
beyond position 1 in Simplify[(1/2)(-a d + a r - Sqrt[4 a^2 d r + (a d -
a r)^2],<<1>>].
An option must be a rule or a list of rules.

Out[8]:= Simplify[1/2(r*a - a*d - Sqrt[4*r*a^2*d + (-r*a + a*d)^2]),
a > 0 && r > 0 && d > 0]

instead of what you get. Got any clue? Seems mi version doesn't like
this kind of options after simplify...

>You just need to specify some assumptions for Simplify or FullSimplify to
>use:
>
>In[10]:=
>Simplify[1/2(r*a - a*d - Sqrt[4*r*a2*d + (-r*a + a*d)2]),
>  a > 0 && r > 0 && d > 0]
>Out[10]=
>-a d
>
>-matt
>
>
>
>
>
>djago at my-deja.com <mailto:djago at my-deja.com> on 11/21/2000 11:55:51 PM
>
>To:   mathgroup at smc.vnet.net <mailto:mathgroup at smc.vnet.net>
>cc:
>Subject: [mg26109]  [mg26062] Simplifying with positive constants
>
>
>
>I'm trying to calculate some results and when I evaluate them I get:
>1/2(r*a-a*d-Sqrt[4*r*a2*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!

```

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