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Groups > comp.soft-sys.math.mathematica > #1805
| From | Mark McClure <mcmcclur@unca.edu> |
|---|---|
| Newsgroups | comp.soft-sys.math.mathematica |
| Subject | Re: solution |
| Date | 2011-04-21 07:10 +0000 |
| Organization | Steven M. Christensen and Associates, Inc and MathTensor, Inc. |
| Message-ID | <iool8j$bn8$1@smc.vnet.net> (permalink) |
On Tue, Apr 19, 2011 at 6:56 AM, amelia Jackson <meli.jacson@gmail.com> wrote:
> I have a problem. I want to find solution:
> r := Table[
> k /. FindRoot[BesselJ[0, k] + k BesselJ[1, k] == 0, {k, n}], {n, 1, 100}]
>
> but I get about 30 roots. I need about 100 or more.
As others have pointed out, knowledge of the asymptotic behavior of
the roots of the Bessel functions enable a very efficient solution
with FindRoot. Here's an approach using NSolve requiring a little
less sophistication on the part of the user:
z /. NSolve[BesselJ[0, z] + z BesselJ[1, z] == 0 && 0 < z < 315, z]
MM
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Re: solution Mark McClure <mcmcclur@unca.edu> - 2011-04-21 07:10 +0000
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