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Equation not solving in Mathcad

JH_9781973
5-Regular Member

Equation not solving in Mathcad

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?

 

 

1 ACCEPTED SOLUTION

Accepted Solutions

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

 

View solution in original post

10 REPLIES 10
LucMeekes
23-Emerald III
(To:JH_9781973)

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

 

 

JH_9781973
5-Regular Member
(To:LucMeekes)

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.

 

 

 

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

 

JH_9781973
5-Regular Member
(To:Werner_E)

Thanks Werner for information now I got it 

 

 

Hi,

Welcome to the forum.

Out of interest what was the original math homework question?

Cheers

Terry

LucMeekes
23-Emerald III
(To:JH_9781973)

The 'behaviour' depends on what is known (numerically defined) and what not. Any variables that are numerically defined are replaced by those numbers. So with X, Y and Z not numerically defined you  may get:

LucMeekes_1-1630392957814.png

While, with Y and Z defined:

LucMeekes_0-1630392905782.png

You can undefine variables numerically by self-assigning:

LucMeekes_2-1630393107533.png

And the 'undefinition' applies to symbolics only, so you still can evaluate the result numerically also:

LucMeekes_3-1630393165894.png

 

Success!
Luc

 

P.S. Why can you not attach Mathcad sheet files. Do you get an error message? What is it?

 

Hi,

if you need to upload Mathcad file, then you have to:

  1. pack Mathcad file into zip archive
  2. upload zip archive

 


Martin Hanák
LucMeekes
23-Emerald III
(To:MartinHanak)

That shouldn't be necessary, see attachment.

 

Luc


@LucMeekes wrote:

That shouldn't be necessary, see attachment.

 

Luc


Hi,

... and what about .xmcd and .mcdx ?


Martin Hanák


@MartinHanak wrote:

@LucMeekes wrote:

That shouldn't be necessary, see attachment.

 

Luc


Hi,

... and what about .xmcd and .mcdx ?


No problem, either - see attach.

Mathcad attachments used to be a problem here but this bug was fixed quite a while ago.

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