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# undefined variable problem

## undefined variable problem

(OP)
Hi, I have 3 equations and 3 unknown variables (a11, a13, a31), and cant get results with mathcad. I am obviously doing something wring, can you help? heres a screen of my problem:

http://www.imagebam.com/image/6027a2124806713

### RE: undefined variable problem

There is so much wrong with your example, did you look at the help?  There are some good examples in the quicksheets under "solving equations".

The syntax is not Find(x,y,z)=  it is SomeVar(x,y,z):=Find(x,y,z).  Now you can use SomeVar by putting in a guess for x, y, and z and SomeVar2i:=SomeVar(x,y,z)

David

### RE: undefined variable problem

(OP)
are you shore my example is wrong? I manage to get solution. things that I am looking for are x,y and z.
Heres my last result, do you think is correct?
http://www.imagebam.com/image/9fb461124845595

### RE: undefined variable problem

Are you trying to find a symbolic solution?  If so, you're not using the symbolic equality.  If you're trying to find a numerical solution, you've not defined the coefficients and constants in your equations.

In the future, post the file, not a picture of the file.  No one wants to re-type equations that you've already typed in.

### RE: undefined variable problem

Is this for school?

### RE: undefined variable problem

(OP)
no, its work. I need to gain some results by using Rayleigh-Ritz method on plates. I can get these results by using paper and pen, but I need to be shore that results is correct...

### RE: undefined variable problem

OK, so your sheet produces an answer already, which can be compared with the Cramer's Rule result: http://en.wikipedia.org/wiki/Cramer%27s_rule on the determinants of the coefficients

or, you can substitute the solution back into the original equation and use the symbolic command "factor" to verify that the resultant mess does simplify to the correct quantities.

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