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5 spheres of radius r are inside a right circular cone

Source: Brazilian Mathematical Olympiad 1982 P6

July 27, 2018
geometrysphere3D geometrysolid geometry

Problem Statement

Five spheres of radius rr are inside a right circular cone. Four of the spheres lie on the base of the cone. Each touches two of the others and the sloping sides of the cone. The fifth sphere touches each of the other four and also the sloping sides of the cone. Find the volume of the cone.