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MathGroup Archive 2007

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Re: Guessing "exact" values

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76228] Re: Guessing "exact" values
  • From: "Dana DeLouis" <dana.del at gmail.com>
  • Date: Fri, 18 May 2007 06:09:15 -0400 (EDT)

Hi.  This is not the best solution, but here's one idea I use.
It's not the best solution, because I can't find a way to make Mathematica's
Hyperlinks dynamic.
In other words, once a hyperlink is made (Entered), it appears the address
is locked in stone.
Maybe an expert can jump in and make this dynamic.

A number we know nothing about...(??)
n = 6.283185307179586

Set the variable to something you would like to use.  For me...
NumberToSearch = n; 

Re-Enter this equation (Shift Enter), and then click the link.

Hyperlink["Click Here: Plouffe's Inverter", 
   StringReplace["http://bootes.math.uqam.ca/cgi-bin/ipcgi/lookup.\
  pl?Submit=GO+&number=#&lookup_type=simple", 
     "#" :> ToString[Evaluate[NumberToSearch], InputForm, 
         NumberMarks -> False]]]

The above click shows it might be 2 Pi.

For your example, I took the full value:
n=10.92477796076938

This number didn't work.  Sometimes it won't work if the number is large.
I don't know what "large" means, but the program really works with
fractions.

I decided to divided the number by 3.

NumberToSearch = 10.92477796076938/3
3.641592653589793

If I re-enter the Hyperlink, and click the link, the solution is Pi+1/2.
Multiply by 3 to get your equation.

Reference:  http://pi.lacim.uqam.ca/eng/
-- 
HTH   :>)
Dana DeLouis
Windows XP & Mathematica 6.0 & Help files 5.2 :>~



"Szabolcs" <szhorvat at gmail.com> wrote in message
news:f2eim0$t2f$1 at smc.vnet.net...
> "Another computer algebra system" has a function, identify(), which 
> attempts to guess the exact expression that evaluates to a particular 
> numerical value.
> 
> Example:
> 
> In[1]:= N[3Pi+3/2,10]
> 
> Out[1]= 10.92477796
> 
> > identify(10.92477796);
>                                   3
>                                   - + 3 Pi
>                                   2
> 
> Is there a package with similar functionality for Mathematica?
> 
> Szabolcs
>



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