Can Mathcad 15 solve a symbolic matix?

[ptc-4175781]

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?

[RichardJ]

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

[Werner_E]

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).

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.

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

[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.

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

[ptc-4175781]

I just tried this real quick with no luck again.

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

[RichardJ]

See the attached file

[RichardJ]

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.

[ptc-4175781]

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

[ptc-4175781]

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

[RichardJ]

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

[ptc-4175781]

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.

[Werner_E]

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.

[ptc-4175781]

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!