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Can Mathcad 15 solve a symbolic matix?

ptc-4175781
1-Newbie

Can Mathcad 15 solve a symbolic matix?

MathCad_2.png

I am trying to solve a 6x6 matrix and keep getting errors for symbol not defined so I tried a simple 2x2 and it also gives the same problem. What I am doing wrong?

MathCad_1.png

12 REPLIES 12
RichardJ
19-Tanzanite
(To:ptc-4175781)

Get rid of the numeric assignment on the left. The symbolic processor does not require variables to be defined, but the numeric processor does.

The errors are from the numeric processor because your variables are not defined. You could omit the (useless) assignment x:= as Richard already pointed out, but even with that assignment you should get a symbolic result (whilst the error and red letters still remain).

A.png

I don't know why it seems that you do not get any evaluation whatsoever ??? I am using Mathcad 15 M010, but I don't think it has to to with that revision level.

A way to avoid all the errors is to rewrite the whole thing using function - but thats rather cumbersome.

B.png

If you would go for this option I would suggest to define a function with only two parameters - a matrix A and vector Y rather than using six single values.

WE

RJ: I am not sure what you mean?I just tried to attach the file but I do not see an Attach a File icon.

WE: I need to solve for all 6 unknowns so I am not sure about your last comment. I will try the function approach.

Thanks folks for the help.

RS

MathCad_3.png

I just tried this real quick with no luck again.

I got thinking about the function idea and tried this with no luck.

MathCad_4.png

RichardJ
19-Tanzanite
(To:ptc-4175781)

See the attached file

RichardJ
19-Tanzanite
(To:ptc-4175781)

RJ: I am not sure what you mean?I just tried to attach the file but I do not see an Attach a File icon.

Click on "use advanced editor" at the top right of the edit dialogue.

Found it thanks. Any more ideas on how to solve? I attached the file to the previous reply.

Tried this too. Looks closer. Perhaps the coefficients are not correct. I need to try and find a proven 6x6 to validate the worksheet.

MathCad_5.png

RichardJ
19-Tanzanite
(To:ptc-4175781)

You get "undefined" because the matrix is singular, and cannot be inverted.

That means I have an issue with the Elasticity problem not with MathCAD. I have checked my work but do not see the issue yet. At least I did not spend days trying to invert by hand!

Thanks for the help.

In the worksheet you posted you had my definition of a function x and later you tried your matrix. It should not make any trouble as long as you use x (and also y, c and L) as formal parameters. But you are on the safe side if you delete or disable the function definition of x.

If you write a function and use it don't use y, c, L as actual parameters as y has alreaady a value in your sheet, c will be interpreted as speed of ligth and L as litre.

You missed the parameter p (or has it the value 1 on purpose?).

Anyway - it looks like Mathcad is not able to invert your 6x6 matrix as it is singular - Richard had already pointed that out. So I think its a good idea to check the values.

Final comment: It appears the major issue is the values I was entering into Matrix A. I will have to ask the professor for more assistance. However, you two taught me a lot about MathCAD Matrix and function methods so the entire day spent jacking with this problem was not a TOTAL WASTE of limited time.

Thanks for the help.

Randy

Here is one that did work!

MathCad_1.png

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