正方形作为最特殊四边形,集中了一般四边形的所有性质,既是中心对称图形,又是轴对称图形,对于一道和正方形有关的题目,抓住它的本质特征,进行变式拓展,可以得出许多重要结论,会极大地开阔学生视野,发散学生思维,调动学生积极性和主动性.【例】已知:如图1,正方形ABCD,E,F分别在边BC,CD上,且∠EAF=45°,AE,AF分别交BD于H,G,连接EF.由以上条件,可以衍 Square as the most special quadrilateral, focusing on all the properties of the general quadrilateral, both centrosymmetric graphics, but also axisymmetric graphics, for a square-related topics, to grasp its essential features, to expand variants, you can draw a lot of important CONCLUSIONS It will greatly widen students ’horizons, diverge students’ thinking and motivate their enthusiasm and initiative. [Example] It is known that as shown in Figure 1, the squares ABCD, E and F are on the sides BC and CD, respectively, and ∠EAF = 45 ° , AE, AF, respectively, to pay BD in H, G, EF connection from the above conditions, can be derived