Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Replacement Rule with Sqrt in denominator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114324] Re: Replacement Rule with Sqrt in denominator
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Wed, 1 Dec 2010 02:10:45 -0500 (EST)

It's not a bug (and not really a "feature", either):

   FullForm[1/Sqrt[x]]
Power[x,Rational[-1,2]]

Thus there is no "Sqrt[x] really in 1/Sqrt[x] (the latter being just a 
quick input form), just as there is no "I" in 1+2I.

On 11/30/2010 4:05 AM, Richard Fateman wrote:
> On 11/20/2010 3:11 AM, kj wrote:
>
>>
>> I don't know a way to write the replacement rule so that it works
>> for both Sqrt[x] and 1/Sqrt[x], but maybe someone else does.
>>
>> ~kj
>>
> See
> www.cs.berkeley.edu/~fateman/papers/better-rules.pdf
>
> which describes how one can automatically produce rules that overcome
> this bug in Mathematica.  oops.  I mean rules that overcome this
> "feature" in Mathematica.
>
> RJF
>
>

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


  • Next by Date: Re: How to assume that a function is positive?
  • Next by thread: Re: Replacement Rule with Sqrt in denominator