variation of phase velocity with propagation angle.taflove

Hi.
please i need to represent the phase velocity with wave propagation angle alpha(numerical dispersion allen taflove susan).
Ny=5 S=0.5 delta=1 c=3e8 k(1)=2*pi

k(i+1)=k(i)-((sin(A.*k(i))).^2+(sin(B.*k(i))).^2-C)./(A*sin(2*A.*k(i))+...
B*sin(2*B.*k(i)));


k(1)=2*pi;
A=Dx*cos(alpha)/2;
B=Dx*sin(alpha)/2;
C=(1/S.^2)*(sin(pi*S/Ny)).^2;

Vp=2*pi*c/k(final)

k (final) is the value of k after 2 or three iteration.[/img]