% This is the torus (donut) in 17.6 #48 with a=2, b=4


ParametricSurface(0,2*pi,20,0,2*pi,20,...
		'(4+2*cos(u)).*cos(v)','(4+2*cos(u)).*sin(v)','2*sin(u) +0*v' )

pause

% This is figure 5 in book, page 1118

figure
ParametricSurface(0,4*pi,40,0,2*pi,10,...
		  '(2+sin(v)).*cos(u)','(2+sin(v)).*sin(u)','u+cos(v)' )