A cone of radius r and height h has volume 81π.
(a) Show that the curved surface area of the cone is given by 
.
(b) Find the radius and height of the cone that make the curved surface area of the cone as small as possible.
A cone of radius r and height h has volume 81π.
(a) Show that the curved surface area of the cone is given by .
(b) Find the radius and height of the cone that make the curved surface area of the cone as small as possible.