Solving equations for Bessel functions

I want to use matlab to solve this equation,

the Bessel function of order 1 to 20, My equation is as follows:

jmi=(besselj(m-1, k_i.*a)+besselj(m+1, k_i.*a))./2;

jmo=(besselj(m-1, k_o.*a)+besselj(m+1, k_o.*a))./2;

ymo=(bessely(m-1, k_o.*a)+bessely(m+1, k_o.*a))./2;

f1 = (n_i .*jmi) ./ n_o .* besselj(m, k_o.*a);

f2 = ((besselj(m, k_o.*a).*jmo)+ (bessely(m, k_o.*a).*ymo))/(besselj(m, k_o.*a).^2+ bessely(m, k_o.*a).^2);

h=f1-f2;

[~,loc] = min(abs(h));

disp(lamda(loc));

It is quite different from the expected result. What is the problem?Thanks for help.

Answer 1

[Torsten]

I cannot recover your equation from the code you posted.

Does that help ?

syms x
syms m integer
J = besselj(m,x)

J = 

Y = bessely(m,x)

Y = 

diff(J,x)

ans = 

diff(Y,x)

ans = 

[菲]

Thank you very much. I'll give it a try