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MathGroup Archive 2006

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RE: FindRoot, suppressing complex interval-numbers

  • To: mathgroup at
  • Subject: [mg70898] RE: [mg70870] FindRoot, suppressing complex interval-numbers
  • From: "David Park" <djmp at>
  • Date: Wed, 1 Nov 2006 03:55:09 -0500 (EST)


There are no real roots - not even at such large values of x.

David Park
djmp at 

From: Paul [mailto:pw23 at]
To: mathgroup at

I have the following problem:
Take the simple example

FindRoot[Sin[x] +2, {x, 1.656 10^8, 1.653 10^8, 1.658 10^8},
EvaluationMonitor :> AppendTo[xs, x]]

In the Help we can read: "FindRoot[lhs==rhs, {x, a, a_min, a_max}]
searches for a solution, stopping the search if x ever gets outside the
range a_min to a_max. "

But when I display xs I can see, that there are also two complex
numbers used.

This is a problem if I use a function (in my case a compiled one)
inside FindRoot, which only accepts real numbers.

So how can I suppress the using of complex numbers in FindRoot?

Best regards,

(Mathematica 5.2)

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