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05-23-2013
09:18 PM

05-23-2013
09:18 PM

This expression does not evaluate symbolically

A little file on Klein botle,

try to make a 3d plot using the polynomial form...how can I do it?

Tried to use a solve block and find , but no luck

try to avoid numeric if possible please...

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4 REPLIES 4

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05-24-2013
03:37 AM

05-24-2013
03:37 AM

Re: This expression does not evaluate symbolically

In your polynomial symbolic expressions change the lower case x,y,z to upper case X,Y,Z. Mathcad seems to be getting confused with your previous use of x,y and z. The solution for Z is too big to be seen, but can be used later.

Alan

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05-24-2013
05:31 AM

05-24-2013
05:31 AM

Re: This expression does not evaluate symbolically

Its only the z which causes the problem. Rename it or use z:=z before the symbolic evaluation.

Nevertheless the polynomial form will not plot as desired as it returns a 6-element vector of z-values.

Furhermore, even if you try to construct a function which only return the first element of this vector, you run into troubles as of complex results which 3D plots does not like. You can take the absolute value of Z(x,y)[0 in the definition of f, but you would lose the sign that way and get additional, unwanted regions in your plot.

Here with a more simple example:

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05-26-2013
03:02 AM

05-26-2013
03:02 AM

Re: This expression does not evaluate symbolically

Thanks WE

after doing what alan suggested, I saw the same problem as shown in your file. . I tried to use find() to solve for Z, but there is no one simple guess that the solution converge.. I guess I will just stay with parametric curve

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05-26-2013
02:18 PM

05-26-2013
02:18 PM

Re: This expression does not evaluate symbolically

henry leung wrote:

.. I guess I will just stay with parametric curve

Sure better. Unfortunately Mathcad can't plot implicit functions, neither 3D nor 2D. Thats a long standing wish.