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From: Rorie Thomson on 22 Dec 2009 11:03
An original post but with developments...
I need to solve three nonlinear equations using bvp4c. the response was given as follows, but i am unsure on a couple things

You said that in each iteration i would need to solve the 4x4 nonlinear system.... do i need to run 4 bvp4c files for each part? I can only find bvp4c examples for equations with one differential in them, not 4 like i have. I understand i can use MATLAB to fsolve, but i do this after i have used bvp4c, correct?

I have seen that when using bvp4c for a problem such as y''+y=0, i would solve for y'=... and work from there using that equation in the bvp4c solver. I am unsure how i should solve my problem for use in the bvp4c solver (or 4 of them depending on your response to the above part) as i have multiple differentials in each equation.

Thanks again

> Use MATLAB's bvp4c and in each iteration when you are
> supposed to supply dT/ds, dx/ds, dy/ds and dy_prime/ds, you would have to solve the (4x4) nonlinear system
> of equations
>
> (1) (dT/ds) - T*((8*(pi^2)*y)/(1-4*(pi^2)*(y^2)))*(dy/ds)
> + 2*pi*y*V =0
> (2) dy/ds - y_prime = 0
> (3) T*(dy_prime/s) + (dT/ds)*(dy/ds) - T*4*(pi^2)*y +
> 2*pi*y*S*(dx/ds) + 2*pi*y*V*(dy/ds) = 0
> (4) (dx/ds)^2 + (dy/ds)^2 + 4*(pi^2)*(y^2) = 1
>
> for the above unknowns dT/ds, dx/ds, dy/ds and dy_prime/ds.
> This could be done using fsolve.
>
> Best wishes
> Torsten.
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