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J
JH_97819738-Gravel
8-Gravel
August 30, 2021
Solved

Equation not solving in Mathcad

  • August 30, 2021
  • 1 reply
  • 5648 views

Dear Community,

 

I am unable to solve a particular equation having a unknown value. After evaluating it is giving the same variable in answer. Any suggestions how to avoid this?

 

 

Best answer by Werner_E

What do you mean by "behavior not identical"?

In your first pic you showed the symbolic evaluation of an equation without using "solve" and so the equation was simply repeated (and a bit simplified).

In your last pic you show an equation symbolically evaluated with "solve,W" and consequently you get the equation solved for W.

This is exactly what Luc showed with your equation. But while you showed a linear equation in your last example, your first example is an equation of order three in w and so Mathcad gives you a vector with the three different solutions of this equation.

And, yes, those solutions are quite ugly:

B1.png

You may assign the result to a function and evaluate it for different values of t:

B2.png

You may also use this function for plotting:

Werner_E_4-1630370069086.png

 

1 reply

L
LucMeekes23-Emerald IV
23-Emerald IV
August 30, 2021

In general you should attach the worksheet, not just a picture.

Other than that: Mathcad did exactly what you asked it to do. You asked a symbolic evaluation of the expression, and you got it: t expressed in terms of w. A bit nicer could be:

LucMeekes_1-1630360405000.png

So here I asked to solve for t.

If I ask it solve for w, I get 3 possible answers (I'll show only part of them):

LucMeekes_2-1630360517789.png

Note that each of the three answers involves t, the (other) unknown.

 

Success!
Luc

 

 

    J
    JH_97819738-GravelAuthor
    8-Gravel
    August 30, 2021

    Thank you Luc for the insight

    But I dont know why the behavior is not identical with other equation attached screenshot (sorry). I tried multiple times to upload the file but could not do so attached the file.

     

     

     

    W
    Werner_E25-Diamond IAnswer
    25-Diamond I
    August 31, 2021

    What do you mean by "behavior not identical"?

    In your first pic you showed the symbolic evaluation of an equation without using "solve" and so the equation was simply repeated (and a bit simplified).

    In your last pic you show an equation symbolically evaluated with "solve,W" and consequently you get the equation solved for W.

    This is exactly what Luc showed with your equation. But while you showed a linear equation in your last example, your first example is an equation of order three in w and so Mathcad gives you a vector with the three different solutions of this equation.

    And, yes, those solutions are quite ugly:

    B1.png

    You may assign the result to a function and evaluate it for different values of t:

    B2.png

    You may also use this function for plotting:

    Werner_E_4-1630370069086.png

     

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