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MathGroup Archive 1996

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Re: Replacement

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4422] Re: Replacement
  • From: wagner at motel6.cs.colorado.edu (Dave Wagner)
  • Date: Mon, 22 Jul 1996 00:09:22 -0400
  • Organization: University of Colorado, Boulder
  • Sender: owner-wri-mathgroup at wolfram.com

Whoops, in my previous post I gave the wrong output:

In article <4snbf1$rra at dragonfly.wolfram.com>,
Dave Wagner <wagner at motel6.cs.colorado.edu> wrote:
>In article <4shud7$g7n at ralph.vnet.net>,
>Sergej Gerassimov <ges at vsnhdd.cern.ch> wrote:
>>
>>x/Sqrt[a^2+b^2]+Sqrt[a^2+b^2]/y //. Sqrt[a^2+b^2]->r
>>gives:
>>
>>      x         r
>>------------- + -
>>Sqrt[a^2+b^2]   y
>>
>>How to replace Sqrt[a^2+b^2] by r everywhere in the expression?
>
>A general solution to this type of problem is to introduce a dummy
>variable and use Solve:
>
>    In[15]:=
>    Solve[{dummy==x/Sqrt[a^2+b^2]+Sqrt[a^2+b^2]/y, r==Sqrt[a^2+b^2]},
>	  {dummy},{a,b}]
>
>    Out[15]=
>	  x         r
>    ------------- + -
>	  2    2    y
>    Sqrt[a  + b ]

That output should have been:

Out[1]=
           x   r
{{dummy -> - + -}}
           r   y

I was cutting and pasting all over the place and I must have inadvertently
included the wrong output in my post.

Sorry for any confusion.

		Dave Wagner
		Principia Consulting
		(303) 786-8371
		dbwagner at princon.com
		http://www.princon.com/princon

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