num

t = 0:pi/20:2*pi;
Ok = [sin(t); cos(t)];
A=[2,1;1,-3];

for i=1:3;
    figure(i);
    Ok2 = A*Ok;
    plot(Ok(1,:), Ok(2,:));
    axis('equal');
    hold on;
    plot(Ok2(1,:), Ok2(2,:));
    k = sqrt(max(Ok2(1,:).^2 + Ok2(2,:).^2));
    Ok = 1/k*Ok2;
    hold off;
end