Help with find root needed

*To*: mathgroup at smc.vnet.net*Subject*: [mg88910] Help with find root needed*From*: Aaron Fude <aaronfude at gmail.com>*Date*: Wed, 21 May 2008 14:49:06 -0400 (EDT)

Hi, In what follows, I'm looking for the largest root of a function, that is also a function of two parameters. The Manipulate command shows me that the root is consistently there (albeit near a singularity which might be what's causing problems). However, FindRoot doesn't find it as the plot shows. I get one error, but my guess is that it's referring to one particular point on the plot. f[z_, h_, \[Gamma]_] := Tanh[h*z] + (\[Gamma]^2 + 1 - z^2)/(\[Gamma]^2 - 1 - z^2) * z/\[Gamma]; Manipulate[ Plot[f[z, h, \[Gamma]], {z, 0, 10}], {h, .1, 10}, {\[Gamma], .1, 10}] K[h_, \[Gamma]_] := z /. FindRoot[f[z, h, \[Gamma]] == 0, {z, 10, 1, 10}]; Plot3D[K[h, \[Gamma]], {h, .1, 10}, {\[Gamma], .1, 10}] Many thanks in advance! Aaron

**Follow-Ups**:**Re: Help with find root needed***From:*"W_Craig Carter" <ccarter@mit.edu>

**Re: Help with find root needed***From:*Darren Glosemeyer <darreng@wolfram.com>