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MathGroup Archive 1999

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Problem with CHasing[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg17946] Problem with CHasing[]
  • From: Andreas Stahel <Andreas.Stahel at hta-bi.bfh.ch>
  • Date: Sat, 5 Jun 1999 02:56:10 -0400
  • Organization: S.u.S.E GmbH, Gebhardtstr. 2, 90762 Fuerth, Germany
  • Sender: owner-wri-mathgroup at wolfram.com

To whom it may concern

I need a package to solve two point boundary value problems.
A while ago I found the package Chasing.m on mathsource and liked what I
saw. Simple to use in simple situations. Unfortunately I came across a
false solution for a very simple problem.
I suspect numerical problems as the reason for the incorrect answer,
as the RHS of the boundary value problem is variing rapidly.


With best regards

Andreas Stahel

-- 
Andreas Stahel, Mathematics, HTA, CH-2501 Biel, Switzerland
Andreas.Stahel at hta-bi.bfh.ch    
Tel 41--32--32 16 258  FAX: 41--32--32 16 500

here is the code leading to a false result.
=========================================================

Clear[f,L,u,un]
f[x_] = Exp[-((x-1.5)/0.3)^2];
L=3;
un[x_] =u[x]/.
	Chasing[{D[u[x],{x,4}]==f[x],
			u[0]==0,u'[0]==0,u[L]==0,u'[L]==0},u[x],{x,0,L}];
Plot[{f[x],un[x]},{x,0,L},PlotRange ->All];
un'[0]

-- 
Andreas Stahel, Mathematics, HTA, CH-2501 Biel, Switzerland
Andreas.Stahel at hta-bi.bfh.ch    
Tel 41--32--32 16 258  FAX: 41--32--32 16 500


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