在说明三角形内角和为180°时,老师让我们作平行线把三个内角“搬”到一起(如图1),利用平角的定义,得到了“三角形内角和等于180°”这个结论.也可以利用对折三角形的方法将三个角“搬”到一起(如图2),利用平角的定义,得到了“三角形内角和等于180°”这个结论.下课前,老师说证明三角形的内角和定理还有很多种方法,让我们课后思考. When explaining that the interior angles of the triangles are 180 °, the teacher lets us parallelize the three interior corners (as shown in Figure 1). By using the definition of a flat corner, we get the interior angle of the triangle and the angle equal to 180 °. This conclusion can also be used to fold the triangle method of the three corners “move ” together (Figure 2), the use of the definition of a flat angle, the "triangle angle and equal to 180 ° The teacher said that there are many ways to prove the interior angles and theorems of triangles so that we can think after class.