function ld()
y=[linspace(0,0,800);linspace(1,1,800)];
x=[linspace(0,3,800);linspace(0,3,800)];
z=[3*sind(linspace(90,0,800));3*sind(linspace(90,0,800))];
mesh(x,y,z);
hold on
z=[3*sind(linspace(90,asind(1/3),800));3*sind(linspace(90,asind(1/3),800))];
mesh(x,y,z);
hold on
z=[4.5*sind(linspace(90,asind(1.5/4.5),800));4.5*sind(linspace(90,asind(1.5/4.5),800))];
mesh(x,y,z);
hold on
z=[4.5*sind(linspace(90,asind(2.5/4.5),800));4.5*sind(linspace(90,asind(2.5/4.5),800))];
mesh(x,y,z);