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MathGroup Archive 2004

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FindRoot in Version 5

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46179] FindRoot in Version 5
  • From: bghiggins at ucdavis.edu (Brian Higgins)
  • Date: Tue, 10 Feb 2004 00:05:48 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

In version 4 I used the following code to solve nonlinear BVP using
NDSolve

system[?_] := {y1'[x] == y2[
    x], y2'[x] == -Sin[y2[x]] + Cos[5x], y1[-1] == 0, y2[-1] == ?};
myODEsoln[?_] := NDSolve[system[?], {y1[x], y2[x]}, {x, -1, 1}]
yend[?_] := (y1[x] /. myODEsoln[?]) /. x -> 1
bc = FindRoot[First[yend[?]] == 0, {?, -2, 2}];
Plot[Evaluate[y1[x] /. myODEsoln[? /. bc]], {
      x, -1, 1}, AxesLabel -> {"x", "y1(x)"}];

In Version 5 is does not work. I have read on this group that FindRoot
was modified so that it now requires that in the above code I replace
yend[Q_] with yend[Q_?NumericQ]. But now the problem is that FindRoot
fails to converge.

So my question: Does anyone know what other modifications have been
made to FindRoot so that I can get this code and many others like it
to work again?

Thanks much

Brian


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