有些課本把下面这个平面的性貭(公理):“如果一条直綫上的两点在一个平面內,那末这直綫上所有的点都在这平面內”作为鉴定一个面(称曲面更合适)是否为平面的准則。事实上这个公理仅仅給出曲面成为平面的必要条件,只有当我們証明了这个条件也是充分条件时,才能确立这个鉴定平面的准則。就直觉 Some textbooks put the following plane’s sexual axioms (axioms): “If two points in a line are in a plane, then all the points in this line are in this plane” as to determine whether a surface (or surface is more appropriate) is The guidelines for the plane. In fact, this axiom only gives the necessary conditions for the surface to become a plane. Only when we prove that this condition is a sufficient condition, can we establish the criteria for this plane of identification. Intuitive