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Re: How to calculate the partial derivative?

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  • Subject: [mg128751] Re: How to calculate the partial derivative?
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Fri, 23 Nov 2012 03:27:53 -0500 (EST)
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When Simplify doesn't work try FullSimplify.

k35 = 1/180 (-b1 b3 - b2 b3 - c1 c3 - c2 c3 - d1 d3 - d2 d3);

k35 = k35 // FullSimplify

(1/180)*((-(b1 + b2))*b3 -
      (c1 + c2)*c3 - (d1 + d2)*d3)


Bob Hanlon

P.S. I am not a professor.


On Thu, Nov 22, 2012 at 8:24 PM, Tang Laoya <tanglaoya1989 at gmail.com> wrote:
> Dear Prof. Hanlon,
>
> Thank you very much for your quick reply.
>
> It is strange that your commands works but mine doesn't work:
>
> k35 = 1/180 (-b1 b3 - b2 b3 - c1 c3 - c2 c3 - d1 d3 - d2 d3)
> k35 = k35 // Simplify
>
> The outputs are:
> 1/180 (-b1 b3 - b2 b3 - c1 c3 - c2 c3 - d1 d3 - d2 d3)
> 1/180 (-b1 b3 - b2 b3 - c1 c3 - c2 c3 - d1 d3 - d2 d3)
>
> respectively.
>
> Could you please help me to take a look at it?
>
>
> Thanks,
> Tang Laoya
>
>
> On Fri, Nov 23, 2012 at 9:12 AM, Bob Hanlon <hanlonr357 at gmail.com> wrote:
>>
>> Use Simplify; however, the specific resultant form is determined by
>> the canonical order of the variables.
>>
>> bb1 = -Det[{{1, 1, 1}, {y2, y3, y4}, {z2, z3, z4}}] // Simplify
>>
>> y4 (-z2 + z3) + y3 (z2 - z4) + y2 (-z3 + z4)
>>
>>
>> -Det[{{1, 1, 1}, {y2, y3, y4}, {x2, x3, x4}}] // Simplify
>>
>> x4 (y2 - y3) + x2 (y3 - y4) + x3 (-y2 + y4)
>>
>>
>> Bob Hanlon
>>
>>
>> On Thu, Nov 22, 2012 at 7:23 PM, Tang Laoya <tanglaoya1989 at gmail.com>
>> wrote:
>> > Dear Prof. Hanlon,
>> >
>> > Thank you very much for your kindly reply for my previous question.
>> >
>> > Now I have another question about factor:
>> >
>> > I wish mathematica give me an express which I can coding by Fortran with
>> > smallest number of floating operations. For example, if I have:
>> >
>> > bb1 = -Det[{{1, 1, 1}, {y2, y3, y4}, {z2, z3, z4}}];
>> >
>> > the result by mathematica is:
>> > y3 z2 - y4 z2 - y2 z3 + y4 z3 + y2 z4 - y3 z4
>> >
>> > I wish it output the result like this:
>> > z2 (y3-y4) - z3 (y2-y4) + z4 (y2-y3)
>> >
>> >
>> > What should I do?
>> >
>> >
>> > Thanks,
>> > Tang Laoya
>
>



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