Re: Debug of FindRoot
- To: mathgroup at smc.vnet.net
- Subject: [mg78888] Re: [mg78871] Debug of FindRoot
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 12 Jul 2007 05:14:09 -0400 (EDT)
- Reply-to: hanlonr at cox.net
With[{Bi = 0.5}, Plot[{Bi*BesselJ[0, z], z*BesselJ[1, z]}, {z, 0.001, 12}]];
With[{Bi = 0.5}, FindRoot[Bi*BesselJ[0, z] == z*BesselJ[1, z], {z,#}]&/@{1, 4, 7, 10}]
{{z -> 0.940771},
{z -> 3.95937},
{z -> 7.08638},
{z -> 10.2225}}
Bob Hanlon
---- Miguel <misvrne at gmail.com> wrote:
> To resolve one of the heat equations it is necesary to calculate the
> solution of z for BesselJ[0,z]/BesselJ[1,z]==z/Bi, where Bi is the
> Biot number (equal to 0.5, for example).
>
> 1.- Plot[{BesselJ[0,z]/BesselJ[1,z],z/Bi},{z,0.001,12}].
>
> >From this plot I deduce the ranges, more or less, {1,4,7,10}.
>
> 2.- FindRoot[BesselJ[0,z]/BesselJ[1,z]==z/Bi,{z,#}]&/@{1,4,7,10}
> {{z->0.940771},{z->3.95937},{z->0.940771},{z->3.95937}}
>
> I dont understand the reason. With others differents intervals it
> works fine.
>
>