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International Mathematical Olympiad 1960 — Contest Problems Question 7

IMO · International Mathematical Olympiad 1960 — Contest Problems

Question 7

(GDR) A sphere is inscribed in a regular cone. Around the sphere a cylinder is circumscribed so that its base is in the same plane as the base of the cone. Let $V_1$ be the volume of the cone and $V_2$ the volume of the cylinder.

(a) Prove that $V_1=V_2$ is impossible.

(b) Find the smallest $k$ for which $V_1=kV_2$, and in this case construct the angle at the vertex of the cone.