function[ikstarxf]=ikstar_back(dx,dy,ky,kx)

%Forward Differencing on x 
ikstarxf=(-3+4*exp(i*kx*dx)-exp(2*i*kx*dx)/(2*dx);

%Backward Differencing on x
ikstarxb=(3-4*exp(-i*kx*dx)+exp(-2*i*kx*dx))/(2*dx);

%Forward Differencing on y
ikstaryf=(-3+4*exp(i*ky*dy)-exp(2*i*kx*dx))