MathDB
MMO 009 Moscow MO 1935 truncated cone, angle wanted

Source:

July 17, 2019
geometry3D geometryconeregular hexagonhexagonangles

Problem Statement

The height of a truncated cone is equal to the radius of its base. The perimeter of a regular hexagon circumscribing its top is equal to the perimeter of an equilateral triangle inscribed in its base. Find the angle ϕ\phi between the cone’s generating line and its base.