Question: How to find the roots of Bessel's function between -4 and 4 using the newton raphson method in maple?

Hi, I am having a little trouble finding the roots of Bessel's function J0 between -4 and 4 using the newton Raphson method, the main issue I am having is not knowing what to input at a certain point.

f:=x->x-evalf(cos(x));
                     f := x -> x - evalf(cos(x))

> low:=-10;

                              low := -10

> up:=10;

                               up := 10

> step:=1;

                              step := 1

> 
> dp:=5;

                               dp := 5

> 
> for i from low to up-step by step do
> 
>           a:=i:
>           b:=i+step: 
>               
>      if f(a)*f(b) < 0 then           
> 
>          print(`root in interval`,a,b):
>                 
>      fi:
> 
> od: 

                        root in interval, 0, 1

As you can see above I was able to get maple to find me the root interval, 

How would I do the same for Bessel's function? What would I put into f:=