topic Re: Issue with Solve Block in Mathcad Prime 9 in Mathcad

Issue with Solve Block in Mathcad Prime 9

MD_14506269 — Fri, 20 Feb 2026 16:03:33 GMT

I was trying to convert a mathcad 15 file to mathcad prime 9, but I get an error in solving for this variable I placed all my guess values and constraints but it still does not work. Refer to the pictures with the solve block and how it was performed in mathcad 15.Mathcad 15 how it was performedMathcad prime 9.0 error in solve block

Re: Issue with Solve Block in Mathcad Prime 9

Werner_E — Fri, 20 Feb 2026 16:24:28 GMT

I guess you can spot the difference

can't you?

You have a system of three equations and three variables you provide guess values for.

So you also have to solve for all these three variables, not just for one!

Otherwise Prime would use the guess values for x.na and fc and tries to find a solution for fs which fulfills all three equations and obviously can't find such a solution.

Re: Issue with Solve Block in Mathcad Prime 9

MD_14506269 — Fri, 20 Feb 2026 16:49:41 GMT

I originally performed it the way that you are telling me but, refer to the photo below, I got the same error and from videos that I saw I believed this was the correct way to solve in prime.

Re: Issue with Solve Block in Mathcad Prime 9

Werner_E — Fri, 20 Feb 2026 17:15:47 GMT

You may try to assign CTOL a larger value to increase the chance that the integrals converge.

Setting it to a smaller (10^-7) value than 10^-3 as you did decreases the chance.

So why don't you attach both sheets here, the MC15 and the P9 sheet.

Depending on the way you attach and the browser you use you may need to pack them into a zip archive to be allowed to attach them.

Re: Issue with Solve Block in Mathcad Prime 9

MD_14506269 — Fri, 20 Feb 2026 19:13:32 GMT

Just modified the CTOL value and it did not change the issue. I do not have the mathcad 15 file for the original but I attached the pdf for that as well as the sheet for P9.

Re: Issue with Solve Block in Mathcad Prime 9

Werner_E — Sat, 21 Feb 2026 01:18:54 GMT

Main problem was that you used a literal index on x_i while you should have used a vector matrix index.

Another problem was an error in the second solve block equation of the first solve block.

Details see in attached Prime 9 file

Re: Issue with Solve Block in Mathcad Prime 9

MD_14506269 — Mon, 23 Feb 2026 15:44:23 GMT

Thank you for the help now I know for next time! Yes I was going to fix the second solve block after I was able to get the first solve block to work.