Trouble with rkfixed in Mathcad prime 9

[AL_11353852]

Hi

I'm trying to remake an old template for solving a differential equation on a free falling hatch in Mathcad Prime 9. Attached is the old version of the file from Mathcad 15.

When I try to set up the rkfixed command after giving all the same info, I get an error code that the function D, doesn't converge. I've tried a few different ways of doing the substitution in D, but I've never gotten the solver to actually solve anything. It either says that D doesn't converge, that t is undefined, or unexpected error, this is a red underline on D.

Is there a way to make this work?

Any help is much appreciated!

[LucMeekes · Accepted solution]

Welcome to the forum.

Based on your supplied information there's little we can do to help.

1. You should always attach the (or a) Prime worksheet that shows the problem.

2. If you have the Mathcad file, you can have it converted to Prime, using the built in converter in Prime 9. That should result in a  working Prime worksheet.

Success!
Luc.

[Werner_E]

As Luc already said, you can't expect much help if you don't show (by attaching the worksheet(s)) what you actually did.

Best guess is that you may have used the wrong indices for alpha.0 and alpha.1. You have to use the matrix index, not the literal subscript.