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Rapha · #3 November 27th, 2008, 07:42 AM

Hello.

Quote:

So now can you get ode45 to work?

that was very helpful, thank you very much (and yes, i could get ode45 to work).

But actually i kinda screwed it(sorry, i did not exactly realize what my problem was and asked for something different), because my problem is :

$\ddot{x} = x + 2 \dot{y} - 0.9 \frac{x+0.1}{D_1} - 0.1 \frac{x-0.9}{D_2}$

$\ddot{y} = y - 2 \dot{x} - 0.9 \frac{y}{D_1} - 0.1 \frac{y}{D_2}$

with $D_1 = \sqrt{(((x+0.1)^2+y^2)^3)}$

$D_2 = \sqrt{(((x-0.9)^2+y^2)^3)}$

i tried to find the IVP 1. order:

$x_1 = x$

$\dot{x_1} = \dot{x} = x_2$

$y_1 = y$

$y_2 = \dot{y_1} = \dot{y}$

=>
$\dot{x_2} = x_1 + 2 y_2 - 0.9 \frac{x+0.1}{D_1} - 0.1 \frac{x-0.9}{D_2}$

$\dot{y_2} = y_1 - 2 x_2 - 0.9 \frac{y_1}{D_1} - 0.1 \frac{y_1}{D_2}$

I did not realize that there are 4 functions: $y_2(t), y_1(t), x_1(t), x_2(t)$

I still want to solve this by using ode45.

Regards
Rapha