由一些熟知的二维空间的问题,经过类比可以发现,用在三维空间的研究中,它们之间有着极为有趣的相似之处。为此,不妨探索一种由二维推广到三维中去的方法;反过来,可把空间的问题转化为平面的问题,从而沟通平面图形与空间图形及其性质间的内在联系。 From some well-known problems in two-dimensional space, it can be found through analogy that there are extremely interesting similarities between them in the study of three-dimensional space. To this end, we may explore a method that extends from two-dimensional to three-dimensional; in turn, the problem of space can be transformed into a plane problem, thereby communicating the intrinsic relationship between planar graphics and spatial graphics and their properties.