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Re: Re: Radicals simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106442] Re: [mg106439] Re: Radicals simplify
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Wed, 13 Jan 2010 05:55:20 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <hic37h$5ef$1@smc.vnet.net> <201001111030.FAA23508@smc.vnet.net> <higdmv$kir$1@smc.vnet.net> <201001121016.FAA16958@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Yes, that's more informative than the documentation extract I quoted -- 
although hardly complete and definitive.

On 1/12/2010 5:16 AM, dh wrote:
> Hi Murray,
>
> stright from the manual:
>
> "With the default setting ComplexityFunction->Automatic, forms are
>
> ranked primarily according to their LeafCount, with corrections to treat
>
> integers with more digits as more complex."
>
> Daniel
>
>
>
> Murray Eisenberg wrote:
>
>> Mathematica 7 documentation does NOT say that LeafCount is the criterion
>
>> for determining simplicity, that is, the default value of
>
>> ComplexityFunction.  Rather it says:
>
>>
>
>>     "The default ComplexityFunction counts the subexpressions and digits
>
>> of integers."
>
>>
>
>> But it does not even say how it combines the counts of the number of
>
>> subexpressions and digits of integers!
>
>>
>
>> On 1/11/2010 5:30 AM, dh wrote:
>
>>> Hi,
>
>>>
>
>>> why do you think x(x^2 y^3)^(1/4) is simpler than (x^6 y^3)^(1/4)?
>
>>>
>
>>> Mathematica needs some criterion for this decision. The default criterion is the
>
>>>
>
>>> "LeafCount[..]". If that does not suit you, you must define another
>
>>>
>
>>> criterion.
>
>>>
>
>>> Daniel
>
>>>
>
>>>
>
>>>
>
>>> francix wrote:
>
>>>
>
>>>> Hi,
>
>>>> I am using Matematica 7 and need some help with Radicals.
>
>>>> If I do
>
>>>> Simplify[(x^4 y^3)^(1/4), x>= 0] I correctly have
>
>>>> x (y^3)^(1/4)
>
>>>> But If I do
>
>>>> Simplify[(x^6 y^3)^(1/4), x>= 0] I get
>
>>>> (x^6 y^3)^(1/4) and not the correct answer  x(x^2 y^3)^(1/4)
>
>>>> Thanks in advanced.
>
>>>
>
>>>
>
>>
>
>
>

-- 
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


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