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Sergey15-Moonstone
15-Moonstone
June 4, 2019
Solved

Symbolic derivative

Hello,

 

I am trying to evaluate the derivative of a function symbolically.

Would anybody, please, help me with this issue?

 

Best regards,

Sergey

 

LucMeekesAnswer
23-Emerald IV
June 4, 2019

You have to define x(t), that is, use ': ' to get ':=', not set it as a boolean (bold =),.

 

Success!

Luc

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16 replies

-MFra-21-Topaz II
21-Topaz II
June 4, 2019

Hi,

before the symbolic derivative you must use clear(A), clear(B), clear(t), clear(omega) or also clear(A,B,t,omega), furthermore you have to use the definition symbol " : " for the function definition and not the equal to "=", as Luc says in his post.

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    Sergey15-MoonstoneAuthor
    15-Moonstone
    June 4, 2019

    Hello,

     

    Thanks for reply.

    As long as I can see, it doesn't work.

    Would you please use my .mcdx file and apply your suggestion properly?

     

    Sergey

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    LucMeekes23-Emerald IVAnswer
    23-Emerald IV
    June 4, 2019

    You have to define x(t), that is, use ': ' to get ':=', not set it as a boolean (bold =),.

     

    Success!

    Luc

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      Sergey15-MoonstoneAuthor
      15-Moonstone
      June 4, 2019

      Hei,

       

      I used "clear (A)" and then defined "x(t)" as you advised. It worked.

      Mathcad's results are complying with my beforehand calculated values.

       

      Thanks a lot.

       

      Best regards,

      Sergey

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      Werner_E
      Werner_E25-Diamond I
      25-Diamond I
      June 4, 2019

      If your goal is to find the derivative but use the value of B you defined and the value of A you found using the solve block, the attached sheet should help.

      What had to be changed:

      1) B (and possibly x, which later is overwritten by function x) should be defined outside of the solve block

      2) no need for x=1 in the solve bock as x IS 1

      3) clear variable t (at least for symbolics) - you don't want it to be 0s anymore

      4) Make the result of the solve block usable for the symbolics by using the inline evaluation "trick"

       

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      LucMeekes23-Emerald IV
      23-Emerald IV
      June 4, 2019

      Sergey uses Prime < 5...

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      Werner_E
      Werner_E25-Diamond I
      25-Diamond I
      June 4, 2019
      @LucMeekes wrote:

      Sergey uses Prime < 5...

      Too bad. Sergey did not mention that.

      Here is a pdf printout of the sheet, in case Sergey is still interested.

       

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