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MathGroup Archive 1997

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Re: Differential Equations system

  • To: mathgroup at smc.vnet.net
  • Subject: [mg6307] Re: [mg6248] Differential Equations system
  • From: seanross at worldnet.att.net
  • Date: Sat, 8 Mar 1997 00:26:31 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

> > > =?ISO-8859-2?Q?Ryszard_Wi=B6niowski?= wrote:
> > > >
> > > > How I can solve the following equations system:
> > > >
> > > > {y''[t]=3D=3D-g-a*y'[t]+b*x'[t],
> > > >  x''[t]=3D=3D-a*x'[t]
> > > > }
> > > >
> > > > or this:
> > > > {
> > > >   y''[t]=3D=3D-g-(a/y[t])*y'[t],
> > > >   x''[t]=3D=3D-a/y[t]*x'[t]
> > > > }
> > > >
> > > > Richard
> > >I think you need to re-state your question.  If y''[t]=3D and 3D is a
 constant, then you have a parabola.  If 3D=3D-X, then
 X is identically zero.  The answer to the first system is that
 x and y are constants.  The answer to the second Is that y is a 
constant and x is identically zero.  I am guessing, though, that that is 
not what you intended.  Remember that there is no substitute for pencil 
and paper.  Before attempting solution on the computer, do the best you 
can to reduce the problem algebraically.


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