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May 12, 2020
09:19 AM

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May 12, 2020
09:19 AM

Non linear coupled differential equation system

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)

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5 REPLIES 5

May 12, 2020
10:26 AM

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May 12, 2020
10:26 AM

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

May 12, 2020
11:31 AM

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May 12, 2020
11:31 AM

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

May 12, 2020
11:56 AM

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May 12, 2020
11:56 AM

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

May 12, 2020
12:49 PM

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May 12, 2020
12:49 PM

Hi Alan,

attached is the OP's file for Prime2.

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

Luc

May 13, 2020
05:15 AM

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May 13, 2020
05:15 AM

Thanks Luc,

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

.

Alan