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“三角形内角和”是我们都很熟悉的教学内容,下面是两位教师的导入设计。【导入设计1】出示学生熟悉的两把三角尺(如图1)。提问:算算这两把三角尺3个内角的和分别是多少度?师生一起列式计算:90°+45°+45°=180°,90°+30°+60°=180°。接着,教师抛出研究主题:同学们已经知道了直角三角形的内角和是180°,那其他三角,3个内角的和也都是180°吗?请各学习小组将课前准备的3个三角形纸片(钝角三角形、直角三角形、锐角三角形各一个)
“Triangle and ” is a familiar teaching content, here is the introduction of two teachers. 【Import Design 1】 Students are familiar with the two triangular ruler (Figure 1). Question: Calculate the sum of the three internal angles of the two trigonomets, respectively, how many degrees? Teachers and students together with the column type calculation: 90 ° +45 ° +45 ° = 180 °, 90 ° +30 ° +60 ° = 180 °. Then, the teacher dished out the research topic: Students already know that the interior angle of a right-angled triangle is 180 °, and that of the other triangles, the interior angles of the three interior angles are all 180 °. Please ask each study group to take the 3 triangles Paper (obtuse triangle, right triangle, acute triangle each one)