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K
kpilested1-Visitor
1-Visitor
October 7, 2014
Solved

symbolic solver Prime 3 vs MC15, what is happening?

  • October 7, 2014
  • 5 replies
  • 2526 views

I am trying to solve for TP57, and in Mathcad 15, I select TP57, select symbolic, variable, solve and get the below result, which seems reasonable.

M15SolveTP57.JPG

I now have MathCAD prime 3, which does produce a nicer looking document, but what is happening here?MP3SolveTP57.JPG .. why is the result so drastically different ?

is there anything I can do, besides reverting to old MathCAD15 to solve a symbolically?

thanks

Kasper

Best answer by RichardJ

It is picking up you numeric assigments for the variables. Type clear.sym(R.Pu,R.SW,....etc), above your symbolic evaluation.

5 replies

Werner_E
Werner_E25-Diamond I
25-Diamond I
October 7, 2014

The symbolic solver (muPad) was not changed when going from Mathcad to Prime.

What has changed is that the non-dynamic way of using the symbolics via the menu is not offered anymore by Prime.

You would encounter the very same effect in Mathcad 15, too, if you use the symbolic evaluation as you had done in Prime.

The reason is, that you have assigned values to your variables and the symbolic evaluation respects those values and units. Because the symbolics does not know anything about units, it treats them as unknow variables. Therefore the symbolics is not able to cancel Ohm and kOhm.

Way out is to clear the values of those variables - either clear them completely using clear() or cleatr them just for use with the symbolics (which is what you need here) - The command ist clear.sym - look it up in the help.

R
RichardJ19-TanzaniteAnswer
19-Tanzanite
October 7, 2014

It is picking up you numeric assigments for the variables. Type clear.sym(R.Pu,R.SW,....etc), above your symbolic evaluation.

K
kpilested1-VisitorAuthor
1-Visitor
October 7, 2014

the clear command made it work.

thank you

TP57+Fixed.JPG

is there a way to reload the cleared values after the solving, as I use them further down the document?

Werner_E
Werner_E25-Diamond I
25-Diamond I
October 7, 2014

Kasper Pilested wrote:

the clear command made it work.

thank you

is there a way to reload the cleared values after the solving, as I use them further down the document?

Use clear.sym(...) (sym is a literal subscript), not just clear(...). That way the values remain valid for numeric evaluation.

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