MATLAB MATLAB - solving equation with Bessel function

[kravky]

Hello,

i am trying to solve this equation for x

besselj(0,0.5*x)*bessely(0,4.5*x)-besselj(0,4.5*x)*bessely(0,0.5*x) ==0;

I tried vpasolve, but it gave me answer x=0 only. fzero function didnt work, too.
What function can solve this equation?

Thanks

 

[Orodruin]

Please show us exactly the code you have tried. Otherwise it is impossible to tell where you might have gone wrong. fzero works perfectly fine for me.

 

[kravky]

Yes. I misused fzero function. now it works for me aswell!

function ffu = f(x)
ffu = besselj(0,0.5*x)*bessely(0,4.5*x) - besselj(0,4.5*x)*bessely(0,0.5*x);

and fzero

fun=@f
x0=2;
S=fzero(fun,x0)

will find solution. It finds only one solution which is close to the x0 value but its not the problem.

 

[Orodruin]

Yes, fzero finds just one solution. It will find different solutions depending on your x0 input.

Also, when you have such a short and simple function, you can just as well define an inline function instead of writing an entire function file.

 

[kravky]

I understand. A good way is to use ezplot as well for a rough estimation of points, where functions is zero (intersection with x axis) and then use this rough guess as x0 input in fzero for precise value