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Thread Subject:
Diferential Equations

Subject: Diferential Equations

From: mona

Date: 22 Mar, 2012 21:31:18

Message: 1 of 2

 
Hello
I need to solve the following Diferential Equations using matlab

(?x/?t)-(t/2)(?z/?t )=0

 [x(?y/?t)-(t/2)z(?y/?t)-(1/2)yz]=(-1/2)y+((?^2 y)/( ?^2 t))

 [x(?z/?t )-(t/2)z(?z/?t)]=(((?^2 y)/( ?^2 t)))
where

x(0)=0; y(0)=0; z(0)=0


I am not new with matlab I tried to reduce the order and Igot system of first order Diferential Equations to use ode45 but the intial condition not enough because I need
x'(0);y'(0);z'(0)

I tried many times to the code but Icoudnot

any help please

muna

Subject: Diferential Equations

From: Roger Stafford

Date: 22 Mar, 2012 22:18:32

Message: 2 of 2

"mona " <iee2006@yahoo.com> wrote in message <jkg5n6$kc9$1@newscl01ah.mathworks.com>...
> Hello
> I need to solve the following Diferential Equations using matlab
>
> (?x/?t)-(t/2)(?z/?t )=0
> [x(?y/?t)-(t/2)z(?y/?t)-(1/2)yz]=(-1/2)y+((?^2 y)/( ?^2 t))
> [x(?z/?t )-(t/2)z(?z/?t)]=(((?^2 y)/( ?^2 t)))
> where
> x(0)=0; y(0)=0; z(0)=0
>
> I am not new with matlab I tried to reduce the order and Igot system of first order Diferential Equations to use ode45 but the intial condition not enough because I need
> x'(0);y'(0);z'(0)
> .......
- - - - - - - -
  You will need one more initial condition to uniquely determine a solution to these equations. That is because the equations have the second derivative of y. To use 'ode45' you will have to first solve for dx/dt, dy/dt, dz/dt, and d^2y/dt^2 in four equations. Unfortunately the denominator, x-t*z/2, that will be present in the equations starts out as zero, so I'm not sure 'ode45' can handle that.

Roger Stafford

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