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Re: System of ODE

  • To: mathgroup at smc.vnet.net
  • Subject: [mg41977] Re: System of ODE
  • From: "Will Self" <wself at msubillings.edu>
  • Date: Mon, 16 Jun 2003 03:56:23 -0400 (EDT)
  • References: <bc7op7$6cb$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Amedeo" <wallpeer at libero.it> wrote in message
news:bc7op7$6cb$1 at smc.vnet.net...
> Hello everyone....
> I want to solve a sytem of ordinary differential equation....the
coefficent
> of this system are Matrices....I try to find in help but I don't find any
> result....
>
> the system is  in this form
>
>  A'[t] = D[t]*A[t]+2*C with a initial condition A[0] = {0,0}
> and t's gap {t,0,300}
>
> I try to write this with NDSolve but it return me a error
> NDSolve[{A'[t] = D[t]*A[t]+2*C,A[0] = {0,0}},A,{t,0,300}]
>
> Naturally D[t] is a matrix 2x2 and C is a columm of 2 element
>
> the dimension of matric  D and C are ok
> but i don't know if i should declare A[t] as a variable matrices....
>
> the error that return NDSolve is
>
> NDSolve::deql : The First argument must have both an equation and an
initial
> condition.
>
> thanx for help
> -- 
> AMS
> Michelin@ingegneriaPOINTunimePOINTit

1.  Write A[t_]={x[t],y[t]} and rewrite the problem as two separate
equations involving x'[t] and y'[t].

2.  Quit using capital letters.  The letter D is reserved in Mathematica and
even if you get everything else right, that will still cause things to go
wrong.

3.  This is irrelevant if you follow my suggestion in (1.), but to multiply
a matrix by a vector or another matrix, you have to use the dot.  If m and
mm are matrices, mm*m is just coordinatewise multiplication.  mm.m is the
matrix product.



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