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为帮助同学们顺利解决有关平行四边形的判定问题,这里介绍几种思维方法.一、数个数,把握概念例1如图1,在四边形ABCD中,AB∥CD,AD∥BC,E、G、F、H分别为AD、AB、BC、CD上的点,且GH∥AD,EF∥AB,EF、GH相交于点O,则图中共有哪些平行四边形?分析平行四边形的定义是,两组对边分别平行的四边形叫平行四边形.根据这个定义,利用题中的已知条件AB∥CD,AD∥BC,GH∥AD,EF∥AB即可找出图中的平行
In order to help students to successfully solve the problem of parallelogram judgment, here are some ways of thinking: First, a few numbers, to grasp the concept Example 1 In the quadrilateral ABCD, AB∥CD, AD∥BC, E, G , F and H are the points on AD, AB, BC and CD, respectively, and GH∥AD, EF∥AB, EF and GH intersect at point O, what are the parallelograms in the figure? Analysis Parallelogram is defined as two Group parallel to the sides parallel to each other called the parallelogram quadrilateral.According to this definition, the problem using the known conditions AB∥CD, AD∥BC, GH∥AD, EF∥AB can be found in the figure parallel