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