Solving Bessel Functions Homework Questions

skrat
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Homework Statement


Calculate:
a) ##\frac{d}{dx}(xJ_1(x)-\int _0^xtJ_0(t)dt)##
b) ##xJ_1(x)-\int _0^xtJ_0(t)dt##
c) let ##\xi _{k0} ## be the ##k## zero of a function ##J_0##. Determine ##c_k## so that ##1=\sum _{k=1}^{\infty }c_kJ_0(\frac{x\xi _{k0}}{2})##.

Homework Equations


The Attempt at a Solution



a) ##\frac{d}{dx}(xJ_1(x)-\int _0^xtJ_0(t)dt)=xJ_0(x)-xJ_0(x)=0##.

b) What do I do with the integral? Should I calculate ##J_n(x)=\frac{1}{\pi }\int _0^{\pi }cos(tsin\varphi -n\varphi)d\varphi ## for n=0?

c) Hmmm, no idea here :/
 
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skrat said:

Homework Statement


Calculate:
a) ##\frac{d}{dx}(xJ_1(x)-\int _0^xtJ_0(t)dt)##
b) ##xJ_1(x)-\int _0^xtJ_0(t)dt##
c) let ##\xi _{k0} ## be the ##k## zero of a function ##J_0##. Determine ##c_k## so that ##1=\sum _{k=1}^{\infty }c_kJ_0(\frac{x\xi _{k0}}{2})##.


Homework Equations





The Attempt at a Solution



a) ##\frac{d}{dx}(xJ_1(x)-\int _0^xtJ_0(t)dt)=xJ_0(x)-xJ_0(x)=0##.

b) What do I do with the integral? Should I calculate ##J_n(x)=\frac{1}{\pi }\int _0^{\pi }cos(tsin\varphi -n\varphi)d\varphi ## for n=0?

c) Hmmm, no idea here :/

I'm no expert in the theory of Bessel functions, but isn't the expression in part b) just the integral of the entire expression in a) wrt x? Integrating 0 gives you a constant. The constant can easily be found by subbing in a suitable value of x, right?

c) exceeds my knowledge, someone else will have to help, sorry.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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