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Re: FixedPoint[Cos, 1.0]

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  • Subject: [mg119362] Re: FixedPoint[Cos, 1.0]
  • From: David Reiss <dbreiss at>
  • Date: Wed, 1 Jun 2011 04:30:32 -0400 (EDT)
  • References: <is2kjq$qrm$>

Take a look at the comment in the "Possible Issues" section of the
documentation.  This is a "teachable moment" for your students
concerning machine arithmetic and library functions.


On May 31, 7:49 am, J Siehler <jsieh... at> wrote:
> My numerical analysis students this past term pointed out to me that
> the command
> FixedPoint[Cos, 1.0]
> which is the first example in the Information for FixedPoint doesn't
> ever finish running (or, not in any reasonable amount of time).  We
> tried this on serveral versions of Mathematica (6.x, 7.x, and 8.x),
> all on OS X, and got the same nonresult.
> It can be forced by specifying something like FixedPoint[Cos, 1.0,
> SameTest -> (Abs[#1 - #2] < 10^-10 &)] or FixedPoint[Cos, 1.0, 40],
> but it seems like that should be unnecessary, and the form given in
> the documentation should work.  Can anybody else confirm this
> behavior?  Am I missing something totally obvious here?

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