China mathematical olympiad 1995 problem4
Source: China mathematical olympiad 1995 problem4
September 15, 2013
geometry3D geometryspheretetrahedrongeometry unsolved
Problem Statement
Given four spheres with their radii equal to respectively, each sphere externally touches the other spheres. Suppose that there is another sphere that is externally tangent to all those four spheres, determine the radius of this sphere.