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blaubacher1-Visitor
1-Visitor
January 19, 2017
Solved

symbolic algebra and substitution

  • January 19, 2017
  • 1 reply
  • 5773 views

I'm trying to simplify 5 equations by substituting until I have one equation and just a few inputs.  The symbolic result is extremely complex and could easily be simplified but no matter what I try, I can't get it to simplify or collect on terms.  Further, when I later use the derived equation, the numerical value is incorrect.  It is challenging to find where the error is occurring.

Suggestions?

thanks

Best answer by MJG

If the numerical results are different, then the equations are not equivalent.

Are you sure about the 5 initial equations?

By the way, you can perform all the substitutions in one math region:

I included the "simplify" keyword at the end, but it didn't change much from the equation you found.

he result is the same:

1 reply

M
MJG1-VisitorAnswer
1-Visitor
January 19, 2017

If the numerical results are different, then the equations are not equivalent.

Are you sure about the 5 initial equations?

By the way, you can perform all the substitutions in one math region:

I included the "simplify" keyword at the end, but it didn't change much from the equation you found.

he result is the same:

    M
    MJG1-Visitor
    1-Visitor
    January 19, 2017

    After playing a little more, I see that the result should be 0.231, as you noted:

    This seems to indicate that there is a bug in Mathcad's symbolics.

      B
      blaubacher1-VisitorAuthor
      1-Visitor
      January 19, 2017

      Mark, thanks very much for confirming the problem.  I'm certain of the equations and you can see if you use them directly in a solve block or otherwise that the answer should indeed be 0.231.  Can you tell me how you did all the substitutions at once?  That's pretty handy.  It seems that Mathcad prime is quite a bit different than the old mathcad that I'm used to.

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