Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

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

Search the Archive

Re: Re: Hypergeometric2F1

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93258] Re: [mg93156] Re: [mg93136] Hypergeometric2F1
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sat, 1 Nov 2008 05:10:22 -0500 (EST)
  • References: <200810280954.EAA22098@smc.vnet.net> <200810291049.FAA09463@smc.vnet.net> <490ADB4D.6060901@csl.pl> <8A64139D-4377-4DF0-BD6B-A61C7F9744D6@mimuw.edu.pl>

One more thing. When FindInstance returns {} it means that can prove  
that there are no solutions to the problem. This is perfectly reliable  
answer.
When FindInstance cannot decide, it tells you so.

Compare this:

FindInstance[x^4 + y^4 == -z^4 && x y z != 0, {x, y, z}, Integers]
{}

with this:

FindInstance[x^3 + y^3 == z^3 && x*y*z != 0, {x, y, z}, Integers]
The methods available to FindInstance are insufficient to find the  
requested instances or prove they do not exist. >>
FindInstance[x^3 + y^3 == z^3 && x*y*z != 0, {x, y, z}, Integers]


(Besides learning some calculus it might be helpful to learn the  
basics of Mathematica).

Andrzej Kozlowski


On 31 Oct 2008, at 20:21, Andrzej Kozlowski wrote:

> You seem to have missed some of you calculus classes, in particular,  
> when the subject was Taylor's series (that is what + O[x]^5 in my  
> code means).
>
> (As form Fermat's Last Theorem; actually Mathematica knows it:
>
> FullSimplify[x^n + y^n == z^n, Element[x | y | z | n, Integers] && n  
> > 2 && x y z != 0]
> False
> )
>
>
> Andrzej Kozlowski
>
> On 31 Oct 2008, at 19:17, Artur wrote:
>
>> I'm agree that my previous sample wasn't good ArcCosh[2]/ArcCosh[2- 
>> x] with FindInstance (I was think about FindFit (interpolating).
>> The best interpolation known for me is:
>> Plot[{ArcCosh[2]/ArcCosh[2 - x], Hypergeometric2F1[1/2, 2/3, 4/5,  
>> x]}, {x, -4, 1}]
>> I'm looking for better
>>
>> I'm still looking for working procedure procedure for:
>> FindInstance[Hypergeometric2F1[1/3, a/3, 5/6, b/32] == 8/5, {a, b}]
>> what inspite FindInstance ?
>>
>> or
>>
>> FindInstance[2 Cos[2 Pi x] == Hypergeometric2F1[1/2 + a x, 1/2 + b  
>> x, 1/2, 3/4] ,{a,b}]
>>
>> As I was informed earlier procedure of Andrzej Kozlowski don't work  
>> with Hypergeometric2F1
>> e.g.
>> In[1]: FindInstance[ LogicalExpand[
>> 2 Cos[2 Pi x] - Hypergeometric2F1[1/2 + a x, 1/2 + b x, 1/2, 3/4] +
>>  O[x]^5 == 0], {a, b}]
>> Out[1]:{}
>>
>> True answer is {a,b}={-3,3} or {a,b}={3,-3}
>>
>> Because always Andrzej Kozlowski's procedure return {} if is used  
>> with Hypergeometric2F1 we can also prooved with use of them Fermat  
>> Last Theory.
>>
>> Between beliving that procedure work and true working is infinity.
>>
>> Best wishes
>> Artur
>>
>> Andrzej Kozlowski pisze:
>>> On 28 Oct 2008, at 18:54, Artur wrote:
>>>
>>>
>>>> Dear Mathematica Gurus!
>>>> Who know which Mathematica procedure to use to find such a,b,c that
>>>> ArcCosh[2]/ArcCosh[2-x]==Hypergeometric2F1[a,b,c,x] for {x,- 
>>>> Infinity, 1}
>>>> BEST WISHES
>>>> ARTUR
>>>>
>>>>
>>>
>>>
>>> What makes you think such a,b,c exist?
>>> This seems to indicate that they do not:
>>>
>>> FindInstance[LogicalExpand[
>>>         ArcCosh[2]/ArcCosh[2 - x] -
>>>             Hypergeometric2F1[a, b, c, x] + O[x]^5 ==
>>>           0], {a, b, c}]
>>> {}
>>>
>>> Andrzej Kozlowski
>>>
>>>
>>>
>>> __________ Information from ESET NOD32 Antivirus, version of virus  
>>> signature database 3565 (20081029) __________
>>>
>>> The message was checked by ESET NOD32 Antivirus.
>>>
>>> http://www.eset.com
>>>
>>>
>>>
>>>
>



  • Prev by Date: RE: ColorData as a Funnction of height values
  • Next by Date: Re: Graph by Date
  • Previous by thread: Re: Re: Hypergeometric2F1
  • Next by thread: Re: PDE heat equation (inconsisten problem)