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MathGroup Archive 2005

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Re: Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58674] Re: Simplify
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Thu, 14 Jul 2005 02:48:59 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, England
  • References: <db2g9i$djm$1@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 Paul,

Use *PowerExpand* rather than *Simplify* since *Simplify* does not 
expand powers.

In[1]:=
poly = p*(p - 1)*b^2 + s^2

Out[1]=
b^2*(-1 + p)*p + s^2

In[2]:=
prod = Sqrt[poly]*Sqrt[1/poly]

Out[2]=
Sqrt[1/(b^2*(-1 + p)*p + s^2)]*
   Sqrt[b^2*(-1 + p)*p + s^2]

In[3]:=
PowerExpand[prod]

Out[3]=
1

Best regards,
/J.M.


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