平几中有这样一个定理: 定理四边形ABCD中,E、F分别是对角线ACFD的中点,则 可以把上述定理推广到四面体中去: 推广定理四面体ABCD中,E、F分别是棱AC、BD的中点,则 推广定理沟通了四面体两对棱中点的连线段与四面体六条棱之间的关系.利用它可以巧妙、简捷地解决一类立几竞赛题. There is such a theorem in the flat number: Theorem Quadratic ABCD, E, F are the midpoints of the diagonal ACFD, then the above theorem can be generalized to the tetrahedron: The promotion theorem tetrahedron ABCD, E, F are In the midpoints of the edges AC and BD, the promotion theorem communicates the relationship between the line segment of the tetrahedron with two pairs of edges and the six edges of the tetrahedron. It is possible to use it to solve a class of standing contests in a clever and simple manner.