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bmulyanto1-Visitor
1-Visitor
May 22, 2017
Solved

symbolic derivation inconsistency

  • May 22, 2017
  • 1 reply
  • 2154 views

I am trying to write a sheet for grad, div, and curl.

I am finding that one symbol (rho) is considered as a constant instead of a variable.

what should I do to rectify this?

test.jpg

Best answer by Fred_Kohlhepp

Prime has an annoying habit of labeling your variables and constants.  You (apparently) have rho as a constant:

1 reply

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Fred_Kohlhepp23-Emerald IAnswer
23-Emerald I
May 22, 2017

Prime has an annoying habit of labeling your variables and constants.  You (apparently) have rho as a constant:

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    bmulyanto1-VisitorAuthor
    1-Visitor
    May 23, 2017

    Yes...I think prime has this weird behaviour. I changed rho with other symbol and changed it back to rho...and it showed a correct result.

    The thing is I dont always have the opportunity to debug this kind of error..although I have sort of an expected result beforehand.

    Do you have any tips for me?

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    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    May 23, 2017

    As Luc says, the way Prime labels is a mystery to us all.  Prime does format the variable differently from label type to label type, although there are very minute differences.

    The original Mathcad didn't really use labels a lot.  So if you defined a variable m := 24 gm (call the mass the letter m, and assign it the value of 24 grams), Then a little further on defined length := 6 m (define the length to be six meters), what you really told Mathcad was "define the variable "length" and assign it the value of 144 grams." (6 x 24 = 144)

    So when they redid Prime, they used labels; you can have m (as a variable or constant) equal to 24 grams, AND m (labeled as a unit) to represent one meter.

    The result:  They solved one issue and created another.

    Tips?  About this?  When you see something that doesn't seem to make sense, stop and figure it out.  It's usually time well spent.

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