function esempio(caso)

switch caso
    case 1
        n=40; v=linspace(1,n,10); z=zeros(size(v));
        E=1./v;
        clf;
        
        subplot(2,1,1);
        hold on;
        plot(0,0,'ro','LineWidth',1,...
            'MarkerEdgeColor','k',...
            'MarkerFaceColor','r',...
            'MarkerSize',8);
        hold on;
        plot(E,z,'ro','LineWidth',1,...
            'MarkerEdgeColor','g',...
            'MarkerFaceColor','g',...
            'MarkerSize',8);
        
        subplot(2,1,2);
        hold on;
        plot(0,0,'ro','LineWidth',1,...
            'MarkerEdgeColor','k',...
            'MarkerFaceColor','r',...
            'MarkerSize',8);
        hold on;
        plot(v,z,'ro','LineWidth',1,...
            'MarkerEdgeColor','g',...
            'MarkerFaceColor','g',...
            'MarkerSize',8);
        
        hold off;
        
    case 2
        
        n=4;
        Px=[-n n n -n -n]; Px=Px';
        Py=[-n -n n n -n]; Py=Py';
        angles=linspace(0,2*pi,100); 
        angles=[angles 0];
        discx=cos(angles);
        discy=sin(angles);
        
        clf;
        axis square;
        hold on;
        fill(Px,Py,'m');
        fill(discx,discy,'w');
                plot([-n n],[0 0],'k');
        plot([0 0],[-n n],'k');
        hold off;
end