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OT_146132603-Newcomer
3-Newcomer
June 18, 2026
Question

Issue with units when using solve function

  • June 18, 2026
  • 1 reply
  • 5 views

Hello, 

I’m attempting to solve a polynomial using the solve function however my solutions are continually being shown as long expressions rather than singular numbers. I’m fairly confident there’s an issue with the units as some of the units are blacked out in the solver box, see below.

I’ve tried toggling the “Units/Constraints in Symbolic” option as this seems to have helped others with similar problems but that doesn’t seem to be working for me. 

Any suggestions/solutions are greatly appreciated. 

 

1 reply

W
Werner_E25-Diamond I
25-Diamond I
June 18, 2026

The problem which can be seen in the picture is that some “mm” are labeled as unit but some others are labeled as variables. That way the symbolics treats them as different unknowns and is not able to simplify the expression any further. 

Usually turning ON “Using Units/Constants in Symbolics” in the calc options should help with this problem but its necessary to let the sheet recalculate after checking this option. Have you tried doing so?

BTW, if you turn on this option, the symbolics still does not know anything about units but it helps to keep the label “Unit” during symbolic calculation.

If some of your variables would be defined in different length units like a mix of mm, cm and meter, symbolic evaluation still will not be able to simplify the result because it treats mm and cm as two different variables and does not know at all that 1 cm = 10 mm (unless you tell it so either by a definition cm:=10mm or by using the “substitute” modifier in the symbolic evaluation.

That said and seeing that you are just looking for a numeric result I would suggest using numeric methods and not the symbolics. You can either use the “root” command in one of its two flavors or a solve block with “find”.
Look them up in the help and if you experience problems come back and ask again and attach your worksheet if ever possible (state which version of Prime you are using!)
You have a better chance for a fast answer if you post in the “Mathcad” subforum rather than in “PTC Education”.

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