The edge-tangent sphere of a circumscriptible tetrahedron - Yu-Dong Wu and Zhi-Hua Zhang A tetrahedron is circumscriptible if there is a sphere tangent to each of its six edges. We prove that the radius l of the edge-tangent sphere is at least \sqrt 3 times the radius of its inscribed sphere. This settles affirmatively a problem posed by Z. C. Lin and H. F. Zhu. We also briefly examine the generalization into higher dimension, and pose an analogous problem for an n-dimensional simplex admitting a sphere tangent to each of its edges. ✪ ✪ ✪ ✪ ✪ Link tải tài liệu: LINK TẢI TÀI LIỆU Theo LTTK Education
