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MathGroup Archive 1997

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Re: Differential Equations system

  • To: mathgroup at smc.vnet.net
  • Subject: [mg6257] Re: [mg6248] Differential Equations system
  • From: seanross at worldnet.att.net
  • Date: Mon, 3 Mar 1997 01:29:14 -0500
  • 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]==-g-a*y'[t]+b*x'[t],
>  x''[t]==-a*x'[t]
> }
> 
> or this:
> {
>   y''[t]==-g-(a/y[t])*y'[t],
>   x''[t]==-a/y[t]*x'[t]
> }
> 
> Richard

I think you need to re-state your question.  If y''[t]= and is a 
constant, then you have a parabola.  If (whatever), then 
(whatever) 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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