# Positive roots of functions using Bessel functions

• January 1st 2013, 07:22 PM
hannah89
Positive roots of functions using Bessel functions
Hi there,

This is my first time using latex too, so I hope that works

I am trying to use an expression that requires me to find the positive roots to:

$J_{1}(a\alpha _{n})Y_{0}(b\alpha _{n})-Y_{1}(a\alpha _{n})J_{0}(b\alpha _{n})=0$

Now, I have found a table which gives the roots of:

$J_{0}(a\alpha _{n})Y_{0}(b\alpha _{n})-J_{0}(b\alpha _{n})Y_{0}(a\alpha _{n})=0$

for various b/a values.

My question is: does anyone know where to find more tables for other expressions, or - can anyone point me in the right direction for how to find the roots? I had previously posted a similar question but now I think I understand a little more what i'm doing so I've written a new post. I'm basically quite lost and so any help would be greatly appreciated.

a = 1; b = 2; zeros = Quiet[   Table[FindRoot[     BesselJ[0, a*x]*BesselY[0, b*x] -       BesselJ[0, b*x]*BesselY[0, a*x] == 0, {x, n*Pi - .1}], {n, 1,     100}]]; g = x /. zeros; g // TableForm