Surface bounded by the plane z=0, the plane y=z, and the cylinder y=1-x^2 restart: with(plots): Define the top, side, and bottom surface plots. The range for x,y,z is chosen arbitrarily. myrange := x=-5..5, y=-5..5, z=-5..5; top := implicitplot3d( z=y, myrange, color=blue ); side := implicitplot3d( y=1-x^2, myrange, color=red); bottom := implicitplot3d( z=0, myrange, color=green ); Display the surfaces display( {top, side, bottom}, style=patch, axes=boxed); It seems that the range for x, y, and z is too wide. What should the range be to obtain a nicer picture?