Matlab - Script Euler implicito EDOs

L=0.75;

k=25;

M=1.5;

m=0.5;

c=0.25;

U=3.5355339059327;

tol=1e-2;

Z(1,1)=1;

Z(2,1)=0;

h=input('Ingrese salto deseado:');

Tf=30;

T=0:h:Tf;

error=10;

for i=2:length(T)

    F(1,1)=Z(1,i-1)-Z(1,i-1)-Z(2,i-1)*h;

    F(2,1)=Z(2,i-1)-Z(2,i-1)+((k/(M+m))*Z(1,i-1)*h)+((c/(M+m))*Z(2,i-1)*h)-(((L*m*(U^2)*sin(U*(T(i))))/(m+M))*h);

    J(1,1)=1;

    J(1,2)=(h*-1);

    J(2,1)=(k/(M+m))*h;

    J(2,2)=(1+(c/(M+m)))*h;

    Z1viejo=Z(1,i-1);

    Z2viejo=Z(2,i-1);

    while error>tol

        Dz=(-1.*J)\F;

        Z1nuevo=Z1viejo+Dz(1,1);

        Z2nuevo=Z2viejo+Dz(2,1);

        F(1,1)=Z1nuevo-Z(1,i-1)-Z2nuevo*h;

        F(2,1)=Z2nuevo-Z(2,i-1)+Z1nuevo*(k/(m+m))*h+(c/(M+m))*h*Z2nuevo-((L*(U^2)*m*sin(U*(T(i))))/(M+m));

        Z1viejo=Z1nuevo;

        Z2viejo=Z2nuevo;

        error=norm(Dz,inf);

    end

    Z(1,i)=Z1nuevo;

    Z(2,i)=Z2nuevo;

end