三角形中位线定理的证明有很多种方法,如全等三角形法、相似三角形法、坐标法等,本文给出一种“旋转构造”新方法.先看两个基本事实.基本事实1如果一个三角形的三条边长为a、b、c,那么以12a、12b、12c为长度的三条线段也可构成一个新三角形!基本事实2任意三角形绕一边中点旋转180°后 There are many ways to prove the theorem of the median line in the triangle, such as the congruent triangle method, the similar triangle method, the coordinate method, etc. In this paper, we give a new method of “rotation structure” If the three sides of a triangle are a, b, c, then the three segments of length 12a, 12b, 12c can also form a new triangle! Basic facts 2 Arbitrary triangles are rotated 180 ° about the midpoint