Problem with nonlinear solver fsolve??

Hi everyone,

I try to solve

 g=@(x)((0.01783926*sin(0.02077086*x)/7155831.61*x)-1.7519952539)

using fsolve toolbox with this options:

 options=optimoptions('fsolve','algorithm','Levenberg-Marquardt','Display','off');

but it returns x0 that i passed in parameter see this examples:

>> fsolve(g,0.1,options)
ans =
    0.1000
>>fsolve(g,222,options)
ans =
  222.0000
fsolve(g,pi,options)
ans =
    3.1416

how i can choose the x0 to get a correcte solution?

thanks

[Torsten]

Plot your function and you'll find the reason.

Best wishes

Torsten.

[ghazal mohamed]

Ok,Torsten Thank you for your reply.

Answer 1

[John D'Errico]

Note my use of .* in there, to allow vectorized input.

g=@(x)((0.01783926*sin(0.02077086*x)/7155831.61.*x)-1.7519952539)

ezplot(g,[0 5000])
grid on

Se that your function pretty much never crosses zero. Although, if I allow it to go out much further, it could, since the swings oscillate in size proportionally with x.

So I think you have a problem in your function definition.

[ghazal mohamed]

Hi john, thank you for your reply, yes the problem is with the function's expression.