Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

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

Search the Archive

Re: Re: bad performance of Reduce (5.2)


On 22 Jun 2007, at 19:50, m.r at inbox.ru wrote:

> On Jun 17, 5:08 am, Andrzej Kozlowski <a... at mimuw.edu.pl> wrote:
>>
>> On second thoughts: there is probably not much point in testing the
>> condition that Reduce "assumed" numerically  because I am sure Reduce
>> had already done so, and assumed tha tit holds precisely because it
>> passed all numerical tests at its disposal. Nevertheless, I still
>> think that the user should be able to access the full condition that
>> has been assumed, for reasons that seem to me to obvious to need
>> stating.
>>
>> AndrzejKozlowski
>
> It's often convenient to set $MessagePrePrint to InputForm (or unset
> it):
>
> In[1]:= Block[{$MessagePrePrint = InputForm},
>  Reduce[Sin[ArcTan[z] + ArcTan[2*z]] == 1/Sqrt[2] && z > 0, z, Reals]]
>
> During evaluation of In[1]:= Reduce::ztest: Unable to decide whether \
> numeric quantities HoldForm[{(Pi - 4*ArcTan[(-3 + Sqrt[17])/4] - \
> 4*ArcTan[(-3 + Sqrt[17])/2])/4, (3*Pi - 4*ArcTan[(3 + Sqrt[17])/4] - \
> 4*ArcTan[(3 + Sqrt[17])/2])/4}] are equal to zero. Assuming they are.
>
> Out[1]= z == 1/4 (-3 + Sqrt[17]) || z == 1/4 (3 + Sqrt[17])
>
> Maxim Rytin
> m.r at inbox.ru
>
>


Thanks, this indeed can be very useful. Abbreviated messages have  
been a source of irritation for me for many years and somehow I never  
noticed that one could do something about it.

Andrzej Kozlowski


  • Prev by Date: Re: Integrate modified in version 6?
  • Next by Date: general
  • Previous by thread: Re: bad performance of Reduce (5.2)
  • Next by thread: MathLink: letting Mathematica do the hard work