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Mathcad Prime coding issue

tlafata
Newbie

Mathcad Prime coding issue

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.

Screen Shot 2017-04-05 at 11.49.28 AM.png

Screen Shot 2017-04-05 at 11.49.36 AM.png

5 REPLIES 5

Re: Mathcad Prime coding issue

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?

Re: Mathcad Prime coding issue

> 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.

Re: Mathcad Prime coding issue

Hi tj lafata,

you have to do even this small correction:

lafata.jpg

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:

lafata.jpg

lafata1.jpg

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

lafata2.jpg

Many greetings

F. M.

Re: Mathcad Prime coding issue

According to his post yesterday

Re: Mathcad Prime coding issue

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.

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