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## Equation not solving in Mathcad  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  24-Ruby V
(To:JH_9781973)

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: You may assign the result to a function and evaluate it for different values of t: You may also use this function for plotting: 10 REPLIES 10  23-Emerald II
(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: 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): Note that each of the three answers involves t, the (other) unknown.

Success!
Luc  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.  24-Ruby V
(To:JH_9781973)

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: You may assign the result to a function and evaluate it for different values of t: You may also use this function for plotting:   5-Regular Member
(To:Werner_E)

Thanks Werner for information now I got it  20-Turquoise
(To:JH_9781973)

Hi,

Welcome to the forum.

Out of interest what was the original math homework question?

Cheers

Terry  23-Emerald II
(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: While, with Y and Z defined: You can undefine variables numerically by self-assigning: And the 'undefinition' applies to symbolics only, so you still can evaluate the result numerically also: Success!
Luc

P.S. Why can you not attach Mathcad sheet files. Do you get an error message? What is it?  24-Ruby I
(To:JH_9781973)

Hi,

1. pack Mathcad file into zip archive

Martin Hanák  23-Emerald II
(To:MartinHanak)

That shouldn't be necessary, see attachment.

Luc  24-Ruby I
(To:LucMeekes)

@LucMeekes wrote:

That shouldn't be necessary, see attachment.

Luc

Hi,

... and what about .xmcd and .mcdx ?

Martin Hanák  24-Ruby V
(To:MartinHanak)

@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. 