Question

Derive the formula for the curved surface area and total surface area of the frustum of cone.

Answer 1

Let ABC be a cone. A frustum DECB is cut by a plane parallel to its base. Let r₁ and r₂ be the radii of the ends of the frustum of the cone and h be the height of the frustum of the cone.

In ΔABG and ΔADF, DF||BG

∴ ΔABG ∼ ΔADF

CSA of frustum DECB = CSA of cone ABC − CSA cone ADE

CSA of frustum =