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线段、角的加减作为中学数学的基本思想,在初中几何中有广泛的运用,仅在初二几何;“全等三角形”一章中,用到线段、角的加减的习题就有9题之多,所以要求学生能够熟练地掌握,下面以课本上几个题加以说明: (1)已知:如图(1),点E、F在BC上,BE=CF,AB=DC,∠B=∠C。求证:AF=DE。 (2)已知:如图(2),点A、E、F、CD在同一直线上。AD=CB,∠1=∠2,AE=CF。
Line and angle addition and subtraction as the basic idea of high school mathematics, has a wide range of applications in junior high school geometry, only in the second two geometry; “congruent triangle ” chapter, the use of line, angle addition and subtraction exercises As many as nine questions, so require students to master skillfully, the following textbook to explain a few questions: (1) Known: As shown in Figure (1), points E, F in the BC, BE = CF, AB = DC, ∠B = ∠C. Proof: AF = DE. (2) Known: As shown in figure (2), points A, E, F and CD are on the same straight line. AD = CB, ∠1 = ∠2, AE = CF.