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Given Find

mark_neil2
1-Newbie

Given Find

My "Given Find" block that used to work on MC13.1 doesn't work on MC14. Does anyone have an idea why? I have attached the file in MC13 format.

Mark.
8 REPLIES 8

On 1/5/2009 9:18:29 PM, mark_neil wrote:
>My "Given Find" block that
>used to work on MC13.1 doesn't
>work on MC14. Does anyone have
>an idea why? I have attached
>the file in MC13 format.
>
> Mark.

Since you're only asking for a numerical solution, why are you using the symbolic Find?

TTFN,
Eden

because I can see the solution on the same line as "Find". I could have done it in numeric mode. What I am wondering is why this file works fine on MC13 but not on MC14.

Mark.

MC14 has a brand new symbolic processor. It is completely different from that in previous versions of Mathcad. There are many equations (or systems of equations) that are solvable by the Maple based symbolic processor that are not solvable by the new MuPad based symbolic processor (the reverse is also true). You happened upon a system that Maple could solve but MuPad could not. Happens. That's why in general you should not use the symbolic processor unless you actually need its features.
__________________
� � � � Tom Gutman

MC14 needs a helping hand here. Replace the combinations of unknowns in the last equality by the values given previously and it works.

stv

Use complexes or your own abs function.

Alvaro.

stv: thanks. It works in the way that you indicated.
Alvaro: The last condition in your file implies that the imaginary part of the left hand side is zero and its real part is equal to 1. You set the angle of the complex number to zero. Therefore, MathCad generated complex numbers as solutions for some of the parameters. All parameters of the solution should be real numbers. I am looking for the solution that satisfies the "module" of the left hand side is equal to 1 with a non-zero imaginery part.
Also, it looks like it is the symbolic solution that necessitates manipulation of the equations/conditions for MC14 to solve them. if I use numeric solution instead, does it mean that MC14 wouldn't require manipulation of the conditions?

Mark.

On 1/6/2009 12:53:17 PM, mark_neil wrote:
>stv: thanks. It works in the
>way that you indicated.
>Alvaro: The last condition in
>your file implies that the
>imaginary part of the left
>hand side is zero and its real
>part is equal to 1. You set
>the angle of the complex
>number to zero. Therefore,
>MathCad generated complex
>numbers as solutions for some
>of the parameters. All
>parameters of the solution
>should be real numbers. I am
>looking for the solution that
>satisfies the "module" of the
>left hand side is equal to 1
>with a non-zero imaginery
>part.

I know that, but because you're looking only for R and C values, they are reals, giving up the correct real values (if the unknow is f, or some L's or Z's, this method fail, but isn't the case). You can check this with the second method, using the user defined Mag function, that the answer is the same. (This is the reasson to I include this check at the end).

>Also, it looks like it is the
>symbolic solution that
>necessitates manipulation of
>the equations/conditions for
>MC14 to solve them. if I use
>numeric solution instead, does
>it mean that MC14 wouldn't
>require manipulation of the
>conditions?
>
> Mark.

For numerical solution I prefer to reescale the problem, according with the values of TOL (valuing C in pF, for example). Guess values are part of the Given-Find statment, and usually needs to be pretty good ones.

Alvaro.

Alvaro,
I hadn't seen the lower portion of your file. Sorry... It is more clear now. I have defined the Mag function by multiplying the compelx parameter x with its complex conjugate and it takes same length of time for MC14 to find the solution (it didn't make a difference in terms of execution time). Thanks for looking into this.

Mark.
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