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## Re: System of two equations of ODE2

 From: Marco Atzeri Subject: Re: System of two equations of ODE2 Date: Wed, 24 Dec 2014 10:37:26 +0100 User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0

```On 12/24/2014 9:01 AM, ben wrote:
```
```Hi!

The sistem is 2 ODE, whit four initial conditions.

I make this program but it doesn't work.

<http://octave.1599824.n4.nabble.com/file/n4667923/dsf.png>
```
```
1st rule, don't paste image.
It make difficult for us to reply.

the Equation in clearly of second grade as

acceleration=d(velocity)/dt=d2(space)/dt2=-Fgravity/mass

```
```The vector of initial conditions i correct like that? o i have to do

x0=zeros(1,4);

X0(1)=G+h

x0(2)=0

X0(3)=0

x0(4)=vo

i don't know how tho make it.
```
```
as the four variables are
x,y,vx,vy

you can define f as
[dx/dt, dy/dt, d(vx)/dt,d(vy)/dt] =[ vx, vy, -Fx/mass, -Fy/mass]

```
```And another problem i want to plot (x,y), the position vector but it draws
something estrange...
Thanks.
```
```
Regards
Marco

```