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在进行“三角形内角和”这部分内容的教学时,为了讲清“三角形内角和是180°”的道理,我采用了多种方法加以证明,归纳起来有以下六种方法.1.度量法.课前让每个学生剪出不同大小、不同形状的几个三角形.教学时,指导每个学生实际度量各种三角形的三个内角度数,然后算出每个三角形三个内角的度数的和是多少度,使学生从这些感性认识中明白:不论是什么形状的三角形,均有“三角之和等于180°”这一特征.
In the course of teaching “triangle angles and internal angles”, in order to clarify the principle of “triangular angles and 180 degrees in triangles”, I have used a variety of methods to prove and sum up the following six methods. 1. Measure method. Before class, let each student cut out several triangles of different sizes and shapes. When teaching, instruct each student to actually measure the three inner angles of various triangles, and then calculate the sum of the degrees of the three inner angles of each triangle. How many degrees will enable students to understand from these perceptual knowledge: Regardless of the shape of the triangle, there is a characteristic that the sum of triangles equals 180°.