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动态直线和圆的相切问题,是近年中考试卷中的一个新亮点.这类试题即考查学生的动手操作能力和空间想象能力,还考查学生的分类思想、数形结合思想,计算能力等.解决此类问题的主要思路是在动中取静,在静中探静.也就是用运动与变化的眼光去观察和研究图形,把握图形运动的全过程,抓住其中的等量关系和变量关系,灵活运用切线的判定方法,结合所学知识解决问题.灵活运用切线的判定方法,就是根据题目中是否给出直线与圆有公共点的情况,选择不同形式的判定途径.当题设给出直线与圆有公共点时,可根据切线的判
Dynamic tangent and the problem of the circle, is a new bright spot in the examination paper in recent years.This test examines the student's hands-on ability and spatial imagination, but also examines the student's classification of ideas, the number of ideas, computing power. The main idea of solving this kind of problem is to take a quiet while moving and explore the static, that is to observe and study the figure with the vision of movement and change, to grasp the whole process of the figure movement and to seize the equivalent relations and variables Relationship, the use of tangential determination of flexible methods, combined with the knowledge to solve the problem.Use of tangential decision method is based on whether the subject is given a straight line and the circle has a common point, choose different forms of decision-making. Out of the line and the circle has a common point, according to the tangential sentence