%Script file for Figures 4.2(1) (b)

%Figure 4.2(a)

[X,Y]=meshgrid(-1.5:0.1:1.5,-1.5:0.1:1.5);  
Z=X.^2-Y.^2;

figure(1)
[C,h]=contour(X,Y,Z,linspace(-2,2,9));
set(h,'ShowText','on','TextStep',get(h,'LevelStep')*2);

t=linspace(0,2*pi);
xt=cos(t); yt=sin(t);
hold on
plot(xt,yt,'k-');
hold off

Z=X.^3+Y.^2;
figure(2)
[C,h]=contour(X,Y,Z,linspace(-2,2,9));
set(h,'ShowText','on','TextStep',get(h,'LevelStep')*2);

t=linspace(0,2*pi);
xt=cos(t); yt=sin(t);
hold on
plot(xt,yt,'k-');
hold off