how to converge equation

xnew=1;
k0=2*pi/632;
t3=1000;
t2=2000;
n1=1.512;n2=1.521;n3=4.1-1i*0.211;
n4=1;
m=0;


m=0;

k1=k0*sqrt(n1^2-xnew^2);
k2=k0*sqrt(n2^2-xnew^2);
k3=k0*sqrt(n3^2-xnew^2);
k4=k0*sqrt(n4^2-xnew^2);
n=1;
while d>0.0001 & n< 1000
    n=n+1;
    xold=xnew
    k1=k0*sqrt(n1^2-xnew^2);
    k2=k0*sqrt(n2^2-xnew^2);
    k3=k0*sqrt(n3^2-xnew^2);
    k4=k0*sqrt(n4^2-xnew^2);
    
    y=(k2)*t2-atan(k1/1i*k2)-atan((k3/k2)*tan(atan(k4/1i*k2)-k3*t3))+m*pi;
    d=abs(xnew-xold);
end
disp([n,xnew,xold])
 pl show the value  by varying the t3  1 t0 1000
plot(t3,xnew)

[Torsten]

You never update x.

So xold = xnew already in the first step, d=0 and MATLAB consequently exits the while loop.

What do you want to make converge in the above code ?

[shiv gaur]

we want to find root of the equation at which y=0 again by varying the value of t3 the root vary so plot t3 vs xnew

[Torsten]

Then you have to update x according to Newton's method:

xnew = xold - y(xold)/y'(xold)

[shiv gaur]

difficult for derivative of equation

[Torsten]

Why don't you use fsolve to solve

real(y) = 0 and imag(y) = 0 for

real(x) and imag(x) ?

Don't you have a licence for the optimization toolbox ?

[shiv gaur]

pl edit the program