
Re: solution
Posted:
Apr 21, 2011 2:13 AM


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

