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prajendran12-Amethyst
12-Amethyst
April 26, 2021
Question

Mathcad derivative

I'm trying to take the derivative of a function with respect to t but it shows as 0 when it is not. could you please help?

Thanks

Prashanth Rajendran

prajendran_0-1619467299537.png

 

5 replies

LucMeekes23-Emerald IV
23-Emerald IV
April 28, 2021

You've been hit by Prime's infamous autolabelling feature.

The t in the d/dt is labelled an automatic (variable):

LucMeekes_0-1619600418348.png

instead of a real variable:

LucMeekes_1-1619600541232.png

So change its label to variable and all should be as expected.

 

Success!
Luc

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    ttokoro
    ttokoro21-Topaz I
    21-Topaz I
    April 29, 2021

    Prime7 shows no error.

    image.png

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    t.t.
    Werner_E
    Werner_E25-Diamond I
    25-Diamond I
    April 29, 2021

    I can verify the error in Prime 4 and Prime 5 by opening the original sheet and recalculating it (after deleting all the irrelevant and time consuming regions).
    As shown by Luc the workaround is manually labelling the t in the derivative operator as "Variable".

     

    In Prime 6 this bug seems to be fixed - I verified it with both symbolic engines available in P6 (muPad and FreeCAS). So no surprise that its still fixed in P7 😉

     

     

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    prajendran12-AmethystAuthor
    12-Amethyst
    June 6, 2021

    I'm using 3.1 though

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