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最新版人教版教材九年级下册相似三角形的判定,较原版本作了改进.改进一:“平行于三角形一边的直线和其他两边相交,所构成的三角形与原三角形相似.”这是后面所有三角形相似判定定理的基础,但是原版本对此定理只是通过一个特例来说明,学生根本无法证明,无法让学生信服.最新版增加了平行线分线段成比例定理,用平行线分线段成比例定理来证明此定理,使学生信服,也提高了学生的思维能力.改进二:类似直角三角形全等HL的判定方法,增加了思考:斜边的比等于一组直角边的比的两个直角三角形相似吗?
The latest version of the PEP teaching material, Grade 9, is similar to the original triangle, and is improved over the original version. Improvement 1: “The straight line parallel to the triangle intersects with the other two sides, forming a triangle similar to the original triangle.” Is the basis behind all the similarity judgment theorems of triangles, but the original version of this theorem is just a special case to illustrate that students simply can not prove that students can not convince the latest version of the parallel lines divided into segments proportional to the theorem, with parallel lines sub-line segment Proportional theorem to prove this theorem, so that students convinced, but also improve the thinking ability of students.Optimization II: similar to the judgment of rectangular triangle congruence HL, increased thinking: hypotenuse ratio is equal to a set of two Is a right triangle similar?