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MathGroup Archive 1999

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Re: 4th order DE, NDSolve no solution, why?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15813] Re: 4th order DE, NDSolve no solution, why?
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Mon, 8 Feb 1999 03:25:39 -0500 (EST)
  • Organization: University of Western Australia
  • References: <79jcmg$r4a@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Kevin J. McCann wrote:

> That is the first I have seen.  Wonder where I got the idea?  I guess I
> was thinking about eigenvalue problems like
> 
> y''[x] + y[x] == 0, y[0]==0,y[1]==0
> 
> Which NDSolve will do, but it gives y=0 only, not all of the other
> possibilities.

Actually, NDSolve is correct to return y=0 for this problem.  However, I
think you are thinking of

	DSolve[{y''[x]+y[x]==0, y[0]==0, y[Pi]==0}, y[x], x]

which NDSolve can solve.  However, it does not return the general
solution to 

	DSolve[{y''[x]+ n^2 y[x]==0, y[0]==0, y[Pi]==0}, y[x], x]

Cheers,
	Paul

____________________________________________________________________ 
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia            Nedlands WA  6907       
mailto:paul at physics.uwa.edu.au  AUSTRALIA                       
http://www.physics.uwa.edu.au/~paul

            God IS a weakly left-handed dice player
____________________________________________________________________


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