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一课题:三角形内角平分性的线质定理。二教学目的 1.理解定理的含义,初步用来解答一些基本习题; 2.理解定理的证明过程,了解这种证法的基本思想。三重点与难点三角形内角平分线的性质定理及其证明过程是重点;证明定理时适当添作辅助平行线是难点。四教学方法:研究式教学法。五教学过程 1.引入新课教师:如图1,已知△ABC中,AB=AC且AD平分∠BAC;那么BD/DC=? AB/AC=? 〔众生举手,教师指定A生回答。〕 A生:BD/DC=1,AB/AC=1。教师:这两个比有何关系?
A subject: the linear quality theorem of the internal angle of a triangle. Second teaching purpose 1. Understand the meaning of the theorem, initially used to answer some basic exercises; 2. Understand the proof process of the theorem, understand the basic idea of this proof. The property theorem of the bisector of the triangle internal angle and the process of its proof are the key points; it is difficult to prove that the theorem is properly added as an auxiliary parallel line. Four teaching methods: research-based teaching method. V. Teaching process 1. Introduce new teachers: As shown in Figure 1, △ABC is known, AB=AC and AD is divided equally into BAC; then BD/DC=? AB/AC=? [All hands raised, teacher specified A students answer . ] A student: BD/DC=1, AB/AC=1. Teacher: What is the relationship between the two?