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ptc-55060151-Visitor
1-Visitor
January 30, 2015
Question

Problems using solve in Prime 3.

  • January 30, 2015
  • 3 replies
  • 1511 views

Im having problems using the solve function

Sometimes it works fine, other times it does not.

I cannot figuree out what the problem is, but a workaround is sometimes to strip my equations for units. But I rather keep the units.

The problem is that I dont get a result, but MathCad says"This variable is undefined. Check that the label is set correctly". Im not quite sure what it is MathCad is trying to tell me.

Does anyone have a idea of what the problem is and how to work around it?

3 replies

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
January 30, 2015

Well, to start, you're using the symbolic solver to try for a numeric answer. The symbolic solvers are nice (sometimes) but they're not really what Mathcad is good at. (I suggest you learn about numeric solve blocks.)

At any rate, your symbolic solver tried to deal with the units. (The symbolic solver doesn't recongize units, usually.) As a result, your solution with units came out, but it didn't recognize some of the units as units. (A unit has a different font than a variable, so kg can be a unit or a variable,

I copied your symbolic solution, and converted all of the "variables" bach to "units," and there was an answer.

R
RichardJ19-Tanzanite
19-Tanzanite
January 30, 2015

You are using a symbolic solve. The symbolic processor does not know about units, and just sees them as undefined variables. Use a solve block to solve the equation numerically.

R
RichardJ19-Tanzanite
19-Tanzanite
January 30, 2015

If you get rid of the inline evaluation for Iz your symbolic solve correctly picks up on the units and cancels them. Obviously a bug in Prime.

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