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Best answer by Fred_Kohlhepp

Well, sorry Terry, let's rethink this a bit:

Fred_Kohlhepp_0-1674133048903.png

 

2 replies

T
21-Topaz II
terryhendicott21-Topaz II
21-Topaz II
January 19, 2023

Hi,

First and last equations of the four can be rearranged and substituted into second and third equations meaning only two independent equations are used to find four variables and this is not possible.

Capture.JPG

Cheers Terry

    C
    Cornel19-TanzaniteAuthor
    19-Tanzanite
    January 19, 2023

    Here are the solutions obtained in Mathcad 11 with above 4 equations and 4 unknown variables (L1, L2, C1, ws): 

     

    CornelBejan_1-1674123050941.png

    CornelBejan_2-1674123059098.png

    CornelBejan_4-1674123083194.png

    CornelBejan_5-1674123089582.png

    So, these solutions I want to obtained also in Mathcad Prime 7.

     

     

    W
    Werner_E25-Diamond I
    25-Diamond I
    January 19, 2023

    So, these solutions I want to obtained also in Mathcad Prime 7.

     

    Rule of thumb: If you wan to see the result which Maple (the symbolics in MC11) is able to deliver, you should use Maple!

     

    Maple in MC11 was much superior compared to muPad in later versions (up to Prime 6). And muPad on the other hand seems to have been superior to Axom/FriCAS which now is used for symbolic calculations in Prime.

     

    In Prime 6 we can switch over to muPad and also muPad cannot solve your system as it is. But if we do without the last equation (which is independent from the others) and if we help muPad (squaring the two equations to get rid of the roots) it is able to deliver the desired result.

    Werner_E_0-1674133891861.png

     

    But I was not able to talk the new symbolics into delivering a similar result.

    Maybe friCAS in Prime needs even some more manual help, maybe replacing L2 by n*L1 as Fred showed can help. But then why should we use the symbolic engine at all if we have to solve half of the system manually ourselves?

    The point is that it looks to me that you are not using the right tool for the problems you'd like to solve. Your various questions here in the forum ever so often show that the symbolic in Prime simply is not capable enough for your needs even if here and there we could find a clumsy workaround to elicit a reasonable result from Prime after all.

    Its sad but things got worse from Maple to muPad to friCAS.

    Feel free to report this problem here as a bug to PTC support. Then maybe in 10 or 20 years .... who knows?

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    January 20, 2023

    To add to the discussion:

    Mathcad 11:

    LucMeekes_0-1674250084948.png

    Prime 7:

    LucMeekes_1-1674250193740.png

    That error is the 'division by zero' error.

     

    To show the Mathcad 11 result for the second set is valid (given positive values for all knowns):

    LucMeekes_0-1674251524702.png

     

     

    Success!

    Luc

    F
    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    January 22, 2023

    Just to dot an i

     

    Maple (Flow) still can generate the answer:

    Fred_Kohlhepp_0-1674411327377.png

     

    W
    Werner_E25-Diamond I
    25-Diamond I
    January 22, 2023

    Mathcad 15 also has no problems (if we omit the last, independent equation, Neither using the symbolic "solve", nor by symbolically evaluate a solve block with "find".

    Werner_E_0-1674418816430.png

     

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