I have been trying to put Points at the intersection of two curves, one of which is the ouput of a differential equation solved with NDSolve. The output being an Interpolation, NSolve cannot find the intersection coordinates.

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    $\begingroup$ NSolve[] wouldn't be up to the task here, as it's mostly intended for algebraic equations. Why not mention the particular "curves" whose intersections you seek? Maybe the differential equation too, while you're at it... $\endgroup$ – J. M.'s ennui Nov 3 '12 at 16:46
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    $\begingroup$ The docs do mention that "NSolve deals primarily with linear and polynomial equations." Maybe you should try with FindRoot, but that locates one root at a time as it's a fully numerical function. $\endgroup$ – acl Nov 3 '12 at 16:49
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I would use FindRoot in this case. For example:


With the results:

enter image description here

  • $\begingroup$ I could not get FindRoot to work when one functionF"f" is the result of NDSolve and the other function "g"is $\endgroup$ – Jean-Pierre Raynauld Nov 3 '12 at 21:18
  • $\begingroup$ I could not get FindRoot to work when "f" is the output of NDSolve and "g" is a simple function like y=2x! $\endgroup$ – Jean-Pierre Raynauld Nov 3 '12 at 21:20
  • $\begingroup$ @Jean, as you've been told previously, edit your question to include the Mathematica code you already have, including the NDSolve[] bits. $\endgroup$ – J. M.'s ennui Nov 3 '12 at 23:54

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