Non linear coupled differential equation system

[IgorBraz]

Hi, can anynone help me please?!

I'm trying to solve this sistem of two couple differential equations but I'm not getting sucess. (I guess that the error is in the red highlighted in the second equation)

[LucMeekes]

I don't think you can use a derivative in the function vector for a differential system solver.

You may need to expand the vector with one more element.

Success!
Luc

[IgorBraz]

Hi LucMeekes, thanks for your answer.

But how to expand the vector? The problem have two defree of freedom, I don't know how to expand the vector using Rkfixed comand

[AlanStevens]

I can't see your Prime file, but judging by the PNG file, you need to do something like the following:

(for "exolicit" read "explicit" !!!)

Alan

[LucMeekes]

Hi Alan,

attached is the OP's file for Prime2.

I had to zip it, because the forum is running stupid again.

Luc

[AlanStevens]

Thanks Luc,

Attached is my Prime 2 working version (no idea if the results make sense or not!!)

.

Alan