Roots of Bessel first kind function

[Adrian Spiridon]

Hello,

 

        I want to find the firs "s" roots of the function J(alpha, z) - Bessel's first kind function. Suppose alpha=0 , the first 3

roots are: z1=2.4048, z2=5.5201, z3= 8.6537.

        I  have defined  f=@(x)besselj(0,x) and I've tried to use the function fzero but this isn't a viable solution

because fzero needs an interval in wich to search for the root, and at the ends of the interval f must have different signes.   

        Because I don't know how fast the roots may succed,or what the sign of the function is,  I am unable to use fzero

function.   

        Is there any built-in function that can find the zeros of  Bessels's first kind function ? If not (I guess not), how can I

find the roots ? 

      

 

Thanks,

 

Spiridon Adrian