平面几何学习的主要目的是培养学生空 间想象能力和逻辑思维能力,它也是数学竞赛 的重要内容.在命题和解题过程中要特别注意 对图形的各种形状和位置关系的研究,在使用 定理时应根据图形的形状判断题目是否具备 应用定理的条件,否则就可能出现错误,请看 下面的题目. The main purpose of plane geometry learning is to cultivate students’ spatial imagination ability and logical thinking ability. It is also an important content of the mathematical competition. In the process of propositions and problem solving, special attention must be paid to the study of various shapes and positional relationships of graphs, using theorems. When the shape of the graph should be used to determine whether the problem has the conditions of the application theorem, otherwise errors may occur, see the following topics.