四面体是最基本也是最重要的一种几何体,它是三角形在空间的直接推广.四面体的许多性质可以用类比的思想从三角形的性质而得来,如:连接四面体对棱中点的线段交于一点且互相平分;连接四面体任一顶点与它对面三角形重心的线段交于一点G,且这点将所在线段分成的比为3:1,这个点G称 The tetrahedron is the most basic and most important kind of geometry. It is a direct extension of the triangle in space. Many properties of the tetrahedron can be derived from the nature of the triangle using analogical ideas, such as: connecting a tetrahedron to the midpoint of the edge The line segments intersect at one point and are evenly divided; the line segment connecting any vertex of the tetrahedron with the center of gravity of its opposite triangle intersects at a point G, and this point divides the line segment into a ratio of 3:1. This point G is called