Re: Convincing Mathematica that Sqrt[a+b]Sqrt[a-b]==Sqrt[a^2+b^2]

• To: mathgroup at smc.vnet.net
• Subject: [mg63286] Re: Convincing Mathematica that Sqrt[a+b]Sqrt[a-b]==Sqrt[a^2+b^2]
• From: "Jean.Pellegri" <Jean.Pellegri at wanadoo.fr>
• Date: Fri, 23 Dec 2005 05:08:14 -0500 (EST)
• References: <dod6vb\$4fi\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Bonjour

You can define a rule :

In[1 := rule=Sqrt[a_- b_]Sqrt[a_+ b_]->Sqrt[a^2 - b^2]

In[2] := Sqrt[a-b]Sqrt[a+b] /. rule

Out[2] := Sqrt[a^2-b^2]

Jean

"Steven T. Hatton" <hattons at globalsymmetry.com> a écrit dans le message de
news: dod6vb\$4fi\$1 at smc.vnet.net...
> Is there a way to convince Mathematica to multiply Sqrt[a+b]Sqrt[a-b] to
> produce Sqrt[a^2+b^2]?
> --
> The Mathematica Wiki: http://www.mathematica-users.org/
> Math for Comp Sci http://www.ifi.unizh.ch/math/bmwcs/master.html
> Math for the WWW: http://www.w3.org/Math/
>

```

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