本文想就在教学中怎样发挥教师的主导作用,在传授知识的同时积极发展学生的智力,培养能力谈一点粗浅认识。在教学中,对一些典型题,采取固定其中的某些条件、类比变换另一些条件,引导学生对“形异质同”的题目从各个角度进行思考,发挥他们的积极性,不断地进行探讨,从而灵活地掌握解题方法,收到了较好的效果。例如我在指导学生综合运用切割线定理及相似三角形解题时。复习了有关知识及方法之后,安排了一个“同类多变”的题组。例1 如图延长圆的两弦AB、CD交于E点,过E作DA的平行线交CB的延长线于F, This article wants to show how teachers can play a leading role in teaching. While imparting knowledge, they can actively develop students’ intelligence and cultivate abilities to talk a little superficial understanding. In teaching, some typical questions are fixed, some conditions are fixed, and other conditions are changed. The students are guided to think differently from the perspective of “heterogymorphism,” and to use their enthusiasm to continuously discuss. So as to master the problem-solving method flexibly, it has received good results. For example, I was instructing students to use the cutting line theorem and similar triangles to solve problems. After reviewing the relevant knowledge and methods, a “variable” question group was arranged. Example 1 As shown in the figure, the two strings AB and CD of the extended circle are intersected at point E, and the parallel line passing E is DA and the extension line of CB is extended to F.