全文约定:用Ω表示三维欧氏空间的多面体,其顶点集为{A1,A2,…,An},重心为G,令{A1,A2,…,An}={A′1,A′2,…,A′n},由Ω的任意k个顶点A′1,A′2,…,A′k组成的多面体为Ωjk,其重心为Gjk,由Ω的剩余n-k个顶点A′k+1,A′k+2,…,A′n所组成的多面体为Ω—jk,其重心为G—jk(j=1,2,? Full-text convention: use Ω to represent a polyhedron of three-dimensional Euclidean space, whose vertex set is {A1, A2,..., An}, and the center of gravity is G. Let {A1,A2,...,An}={A′1,A′2 ,...,A′n}, a polyhedron consisting of any k vertices A′1, A′2,..., A′k of Ω is Ωjk, its center of gravity is Gjk, and the remaining nk vertices A′k+ of Ω. 1. The polyhedron composed of A’k+2,...,A’n is Ω-jk, and its center of gravity is G-jk (j=1,2,?