Re: NDSolve help
- To: mathgroup at smc.vnet.net
- Subject: [mg43647] Re: NDSolve help
- From: sean_incali at yahoo.com (sean kim)
- Date: Sat, 27 Sep 2003 04:58:09 -0400 (EDT)
- References: <bl0uk1$3vm$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
sashan <mabus at operamail.com> wrote in message news:<bl0uk1$3vm$1 at smc.vnet.net>...
> I'm a newb to mathematica. I'm trying to use NDSolve for a system of 2
> 2nd order ODE's and it complains that the number of initial conditions
> (4) is not equal to the total order of the system (2). But I'm pretty
> sure I've specified all the initial conditions. I've pasted the NDSolve
> code I'm trying to write.
>
> \!\(\(solution\ = \ NDSolve[{\(y''\)[t] == \(-\((\(-\ x[
> t]^2\) + y[t]\ v^2)\)\), \ \(x''\)[
> t] == \(-\((\ x[t] y[t] + x[t] v^2)\)\),
> y[0] == 0, \(y'\)[0] == \(-1\), x[
> 0] == 1, \(x'\)[0] == 0} /.
> v -> \@\(\(x'\)[t]^2 + \(y'\)[t]^2\), {x, y}, {t, 0,
> 200}];\)\)
I can't seem to recreate the problem in Mathematica 5.0 you can use InputForm
to change those symbols to ascii inputform. your problem is as pasted
below
In[1]:=
solution =
NDSolve[{Derivative[2][y][t]\[Equal]x[t]^2-v^2*y[t],
Derivative[2][x][t]\[Equal]-(v^2*x[t])-x[t]*y[t],y[0]\[Equal]0,
Derivative[1][y][0]\[Equal]-1,x[0]\[Equal]1,
Derivative[1][x][0]\[Equal]0}/.v\[Rule]
Sqrt[Derivative[1][x][t]^2+Derivative[1][y][t]^2],{x,y},{t,0,200}]
Out[1]=
{{x\[Rule]InterpolatingFunction[{{0.,200.}},<>],
y\[Rule]InterpolatingFunction[{{0.,200.}},<>]}}
as I said. no errors on Mathematica 5.0 I wonder what the problem is...