close all;
figure,     hold off; plot(Ax_n, Ay_n, 'r-*', 'linewidth', 2); hold on;
plot(Bx_n, By_n, 'b-*', 'linewidth', 2); quiver(Ax_n, Ay_n, Gax, Gay); quiver(Bx_n, By_n, Gbx, Gby);
%for i=1:N, plot([Ax(i) Bx(i)], [Ay(i) By(i)], 'k', 'linewidth', 2);end;