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MathGroup Archive 2005

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Re: Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58680] Re: [mg58669] Simplify
  • From: Pratik Desai <pdesai1 at umbc.edu>
  • Date: Thu, 14 Jul 2005 02:49:06 -0400 (EDT)
  • References: <200507130729.DAA13777@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

paulvonhippel at yahoo wrote:

>I'm having some trouble getting an expression to simplify in an obvious
>way. (There seems to be a long tradition of users posting to this group
>with similar troubles.)
>
>The expression is
>
> poly = p (p - 1) b^2 + s^2
> prod = Sqrt [poly] Sqrt[1/poly]
> Simplify[prod, {0 < p < 1, s > 0, bϵReals}]
>
>which should return one, I think, but doesn't.
>
>I'd be grateful for suggestions.
>
>Thanks!
>Paul
>
>  
>
Hi
If you look at the help on Sqrt you will find this disclaimer
"Sqrt[a b] is not automatically converted to Sqrt[a] Sqrt[b]"
However the next line says
"These conversions can be done using PowerExpand, but will typically be 
correct only for positive real arguments. "

so

If you try this
Clear[p, b, s, prod, poly]
poly[p_, b_, s_] = p *(p - 1) *b^2 + s^2
Sqrt[poly[p, b, s]] *Sqrt[1/poly[p, b, s]] // PowerExpand

 >>1
Best regards
Pratik




-- 
Pratik Desai
Graduate Student
UMBC
Department of Mechanical Engineering
Phone: 410 455 8134



  • References:
    • Simplify
      • From: "paulvonhippel at yahoo" <paulvonhippel@yahoo.com>
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