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Re: what's wrong with this?!!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114934] Re: what's wrong with this?!!
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 23 Dec 2010 03:54:11 -0500 (EST)
  • References: <732015.44033.qm@web26103.mail.ukl.yahoo.com>

First, the information that Reduce has not been modified since version 5 
(which indeed is what the documentation for Reduce suggests) is clearly 
false. In fact Reduce can do things in version 7 that it could not do in 
earlier ones, e.g

Reduce[Sin[x] == x && Abs[x] < 1, x]

x == 0

$Version

"8.0 for Mac OS X x86 (64-bit) (November 6, 2010)"

Reduce[Sin[x] == x && Abs[x] < 1, x]

During evaluation of In[1]:= Reduce::nsmet:This system cannot be \
solved with the methods available to Reduce. >>

Reduce[Sin[x] == x && Abs[x] < 1, x]

$Version

"6.0 for Mac OS X x86 (64-bit) (May 21, 2008)"

So Reduce has certainly been "modified", at least between versions 6 and 
7. In addition there have been bug fixes (which I presume does not count 
as "modification") and some functions called up by Reduce have been 
modified (which again perhaps does not count as a modification of 
Reduce).

However, in this case Mathematica 6.03 gives the same answer as 
Mathematica 8. I can't check what happens with Mathematica 5 as I no 
longer have it installed.

I am curious about the examples you claim work with Mathematica 5 but 
not with 8. Perhaps they only appear to work in 5 (or appear not to work 
in 8)?

Andrzej Kozlowski



On 22 Dec 2010, at 11:18, olfa mraihi wrote:

> So what's wrong with Reduce in Mathematica 5 to get the output =
Element[n | iP, Integers] && n<= iP < 1 + n?
> 
> knowing that Reduce has not been modified in Mathematica 8 so why does =
it give the correct output which is Element[n | iP, Integers] && iP ===
 n?
> I 'm using Mathematica 5 and I'm constrained to use it because some of =
my examples work on Mathematica 5 but not on Mathematica 8.
> 
> Thank you.
>
> --- En date de : Mer 22.12.10, Andrzej Kozlowski <akoz at mimuw.edu.pl> a =
=E9crit :
>
> De: Andrzej Kozlowski <akoz at mimuw.edu.pl>
> Objet: Re: [mg114909] what's wrong with this?!!
> =C0: "olfa" <olfa.mraihi at yahoo.fr>
> Cc: mathgroup at smc.vnet.net
> Date: Mercredi 22 d=E9cembre 2010, 9h48
>
> The output I get (with Mathematica 8) is:
>
> In[76]:= Reduce[Element[{iP, n}, Integers] &&  !iP < n &&
>    Exists[{iPP}, iPP < n && iP == iPP + 1], {iP},
>   Backsubstitution -> True]
>
> Element[n | iP, Integers] && iP == n
>
> Andrzej Kozlowski
>
> On 22 Dec 2010, at 08:36, olfa wrote:
>
> > Hi mathematica community,
> >
> > this is the system to solve:
> > Reduce[
> > Element[{iP, N}, Integers] &&
> > Not[(iP < N)] &&
> > Exists[{iPP}, (iPP < N) && iP == iPP + 1],
> > {iP}, Backsubstitution -> True]
> >
> > the output is:
> > (N | iP) =E2=88=88 Integers && N =E2=89=A4 iP < 1 + N
> >
> > but it should be:
> > iP==N
> >
> > so what's the problem what is missing to get the correct output?
> >
> > thank you very much.
> >
>
>



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