r=[0:0.1: 1]
 THETA=[0:pi/18: 2*pi]
 [R ,T]= meshgrid(r,THETA);
 X=R.*cos(T);
 Y=R.*sin(T);
 Z=sqrt(1-R.^2).*sqrt(10);
 mesh(X,Y,Z);
 hold on
 mesh(X,Y,-Z);
 axis equal