点、线、面是组成几何图形的基本元素。几何课本第一册第2页以“一根拉紧的线、一张纸的褶痕、长方体的一条棱”作为线段的形象;以“电筒、探照灯射出的光线”作为射线的表象。然而,拉紧的绳线和纸均有厚度和宽度,灯源射出的光是一束光枉。至于面的概念就更含糊了。下面介绍两个例子,以求形象化地讲清面无 Points, lines, surfaces are the basic elements that make up the geometry. Geometry textbook first book page 2 “a tightened line, a paper crease, a rectangular parallelepiped” as the image of the line segment; “flashlight, searchlight light” as the ray appearance. However, the tightened strands and paper have thickness and width, and the light from the light source is a light beam. The concept of noodles is even more vague. Here are two examples, in order to vividly tell the truth