Mathcad Prime coding issue

[tlafata]

Hello,

I am new to Mathcad and am getting the error "unable to form derivative matrix" when using OdeSolve. I think I may not be able to use OdeSolve inline like I am doing, so I tried putting it outside of the solve block as well. Can anyone confirm this? And what should I do instead? I appreciate your help. I am re-posting this because I have changed the code since then thanks to help, but am still getting the same issue. The file is attached, and the screenshots are displayed below.

[tlafata]

I fixed part of the issue by using the differential operators in the drop down menu instead of just typing d/dt. However, now i get "units are not compatible". Does anyone see why?

[Werner_E]

> Does anyone see why?

I already told your here: Mathcad Prime 2.0 Coding issue

Two of your summands have a wrong unit / dimension. Somehow you have to check again your equations. Those summands must be divided by liter ot the like.

I just see that in the other thread you wrote that you fixed the problem and found the solution you were looking for.

[-MFra-]

Hi tj lafata,

you have to do even this small correction:

You have to use as a derivative  the operator defined by mathcad. You can't write d/dt Lb(t)...

Assuming that the last term in second member of the second and third equation, is not multiplied by Vl, you have:

or dividing, for example by Vb the last term in second member of the second and third equation, you have:

Many greetings

F. M.

[Werner_E]

According to his post yesterday      Apr 5, 2017 9:07 PM  he found out about the derivative operator himself and according to gis post in the other thread I referred to he already fixed the unit problem.

@ tlafata

You should close this threads to make clear that the problem is already solved.

[-MFra-]

Thanks Werner, I had not noticed the communication of tj lafata, preferring. above all, to find a solution to the problem.

We look forward to the closing of this discussion by tj Lafata.