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Bill_Capehart5-Regular Member
5-Regular Member
April 6, 2021
Solved

"Fun" Results for Mathcad's New (and Legacy) symbolic solver (Mathcad Prime 6)

  • April 6, 2021
  • 1 reply
  • 2974 views

Hi All.

My students and I have been getting some entertaining results with the solver arrow for the example problem below.

With the "new" and "legacy" symbolic solver the results are somewhat "brittle" almost on par with the picture you get when playing with the ariels of an old-style TV set.  The correct answer should be about 0.0265.

 

For example a common result popping up for the NEW solver is this one (but the letters after the % can differ).  Note also that you can get the "Red Box of Shame™️" with some versions (the type of error in this case is highlighted.

New_Solver.png

When using the legacy solver it can be more likely to behave and give the correct answer.  It also sometimes will give the correct answer but add a very negligible imaginary component.  

Old_Solver.png

Ideas her are welcome and PTC probably should give a prize for the most bizarre answer anyone can muster with this problem.


Cheers and Thanks

Bill Capehart

SD Mines

Best answer by LucMeekes

Mathcad 11 / Maple:

LucMeekes_0-1617739794354.png

There apparently are two possible solutions to the problem, when a=2, b=3.7, c=2.51 and W() is the LambertW function.

 

Success!
Luc

 

1 reply

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
April 6, 2021

Mathcad 11 / Maple:

LucMeekes_0-1617739794354.png

There apparently are two possible solutions to the problem, when a=2, b=3.7, c=2.51 and W() is the LambertW function.

 

Success!
Luc

 

    B
    Bill_Capehart5-Regular MemberAuthor
    5-Regular Member
    March 14, 2023

    Apologies for losing this in the fog of time, Luc.  Thanks for this!

    What had us curious is the percentage notation and how the letters will vary from attempt to attempt.  Is there any explanation for that?

     

    Cheers and Thanks again.  
    Bill

     

    B
    Bill_Capehart5-Regular MemberAuthor
    5-Regular Member
    March 15, 2023

    Yes, root(), solve blocks, hand-written ||-functions the students code that do False-Position, Newton, Second and Bisection all work fine with the same root equation.  It's just the symbolic [arrow] solver that produces that behavior.  It's hard to replicate.  Every semester one or two students get it for the canned example we do in class for the same values of Re, & f.  For me it's a curiosity (and an amusement) and not so much of a problem since we have other resources in MCP to do the job.  

     

    Cheers
    Bill

     

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