用变换的观点研究几何是现代数学的一个重要思想方法。一个图形也就是一个点集,两个图形的点之间可以建立对应关系。如果一个平面图形变成另一个平面图形,则新图形叫做原图形的映象。原图形的点在映象中的对应点叫做这一点的象。如果一个图形的每一个点只对应于它的映象的一个点,并 The study of geometry from the perspective of transformation is an important method of modern mathematics. A graph is also a point set, the two graphic points can be established between the corresponding relationship. If one plan changes to another plan, the new one is called an image of the original. The point of the original graphic in the image is called the image of this point. If every point of a graph corresponds to only one point of its image, and