System of 2 second order coupled differential equations with Mathcad

[klem]

Hello,

My problem deals with a system of 2 second order coupled differential equations, Using Mathcad.

I issue a problem with the "D" function (used to solve a differential equation) when there is more than 1 parameter inside.

Here is the system with 2 parameters Teta1 and Teta2 :

I convert this system to have only first order equations :

Then, I can't find other way than making a D matrix with my 2 parameters Teta1 and Teta2

Then, I issue my problem : its seems that I can't put a D function with 2 parameters in rkfixed method.

So, if anybody here can find a way to solve this system, please let me know ! Any other method to solve it is welcome, of course !

Regards

Kevin

[LucMeekes]

How about this:

This all to show that Mathcad is much more powerfull than doing just numerical solutions.

Success!

Luc

[RichardJ]

Then, I issue my problem : its seems that I can't put a D function with 2 parameters in rkfixed method.

Your D function has three parameters, not two. The variable t does not even appear on he RHS, so get rid if it. If that doesn't fix it, please post a worksheet. It's hard to debug a picture.

[AlanStevens]

Here are a couple of methods:

Alan

[StuartBruff]

Kevin Lem wrote:

Hello,

My problem deals with a system of 2 second order coupled differential equations, Using Mathcad.

I issue a problem with the "D" function (used to solve a differential equation) when there is more than 1 parameter inside.

Here is the system with 2 parameters Teta1 and Teta2 :

I convert this system to have only first order equations :

Then, I can't find other way than making a D matrix with my 2 parameters Teta1 and Teta2

Then, I issue my problem : its seems that I can't put a D function with 2 parameters in rkfixed method.

So, if anybody here can find a way to solve this system, please let me know ! Any other method to solve it is welcome, of course !

Regards

Kevin

Did you look at the answers to this question posed on Eng Tips?

System of 2 second order coupled differential equations with Mathcad - PTC: Mathcad - Eng-Tips

The Mathcad 14/15 ODE solvers do not accept a 2D matrix form for the differential equation.  Instead you must recast it as combined vector.

Stuart