复杂非线性方程求零点问题

sigma665

1. clc
   
2. clear
   
3. syms N M
   
4. K3=[1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0;0, 3.975474723*10^10*(0.0000001949404375*N - 1)^(1/2), 0, 12.3, 0, 0, 0, (-4.722675159)*10^10*(1 - 0.0000001122230922*N)^(1/2), 0, 0, 0, -550;1516646116.0, 0, 1, 0, 0, 0, 0, 0, -1, 0, 0, 0;0, 0, 0, 0, 1, 0, -3503184.713, 0, 0, 0, -1, 0;0, 0, 0, -0.00000000811, 0, 0, 0, 0, 0, 8.0*10^(-11), 0, 0;0, 0, 0, 0, 0, -0.000005, 0, 0, 0, 0, 0, 0.000157;3.975474723*10^10*sin(2*pi*M*(0.0000001949404375*N - 1)^(1/2))*(0.0000001949404375*N - 1)^(1/2), 3.975474723*10^10*cos(2*pi*M*(0.0000001949404375*N - 1)^(1/2))*(0.0000001949404375*N - 1)^(1/2), (-12.3)*sinh(2*pi*M), 12.3*cosh(2*pi*M), 0, 0, 0, 0, 0, 0, 0, 0;0, 0, 0, 0, 0, 0, 4.722675159*10^10*sinh(20.0*pi*M*(1 - 0.0000001122230922*N)^(1/2))*(1 - 0.0000001122230922*N)^(1/2), 4.722675159*10^10*cosh(20.0*pi*M*(1 - 0.0000001122230922*N)^(1/2))*(1 - 0.0000001122230922*N)^(1/2), 0, 0, 550*sinh(20.0*pi*M), 550*cosh(20.0*pi*M);1516646116.0*cos(2*pi*M*(0.0000001949404375*N - 1)^(1/2)), (-1516646116.0)*sin(2*pi*M*(0.0000001949404375*N - 1)^(1/2)), cosh(2*pi*M), -sinh(2*M*pi), 0, 0, 0, 0, 0, 0, 0, 0;0, 0, 0, 0, cosh(2*pi*M), -sinh(2*M*pi), 0, 0, 0, 0, 0, 0;0, 0, 0, 0, 0, 0, 0, 0, cosh(20.0*pi*M), sinh(20.0*pi*M), 0, 0;0, 0, 0, 0, 0, 0, 3503184.713*cosh(20.0*pi*M*(1 - 0.0000001122230922*N)^(1/2)), 3503184.713*sinh(20.0*pi*M*(1 - 0.0000001122230922*N)^(1/2)), 0, 0, cosh(20.0*pi*M), sinh(20.0*pi*M)];
   
5. % K3=vpa(K3);
   
6. K5=subs(K3,M,1);
   
7. df=det(K5);
   
8. 
   
9. dff=eval(['@(N)',char(df)]);
   
10. 
    
11. opt=optimset;
    
12. opt.largeScale='off';
    
13. opt.MaxFunEvals=200;
    
14. opt.TolX=1e-10;
    
15. opt.TolFun=1e-10;
    
16. [x,f]=fsolve(dff,3e6,opt)

复制代码

结果如下：
No solution found.

fsolve stopped because the relative size of the current step is less than the
selected value of the step size tolerance squared, but the vector of function values
is not near zero as measured by the selected value of the function tolerance.

<stopping criteria details>


x =

  4.0041e+006 +1.3434e-011i


f =

-5.4836e+082 +9.3127e+086i

明显不对，此乃何故？

zccbest

明显是不收敛，换个初始值试试