《三角形的内角和》是人教【2011】课标版小学数学四年级下册第67页例6的教学内容。新修订改版的教材上,一是突出了对不同类型三角形内角和的引导,以此让学生来证明及理解所有三角形的内角和都是180°;二是凸显“大约”的辩证思考,引发学生通过回顾旧知感悟测量三角形内角和的方法,体验到在实际测量操作中是存在测量误差的。借此在“分析与操作”的环节上寻找更适合探究三角形内角和方法,起到在解决问题中的优化策略。而在教学过程完成后,以触发对此课例的反思在“空间与图形”模块上的教学方法及优化策略的几点启示。 “Triangle and the triangle” is the teaching content of Example 6 taught by the teacher. The new revised version of the textbook, one is to highlight the different types of triangles and the guidance of the internal angle, so that students can prove and understand all the internal angles of the triangle and are 180 °; the second is to highlight the “about” dialectical thinking, Trigger students by reviewing the old perception of triangulation triangulation method and experience the existence of measurement error in the actual measurement operation. In this way, we can find out more suitable angles and methods of triangulation in the aspect of “analysis and operation”, and play an optimization strategy in solving problems. And in the teaching process is completed, to trigger the reflection of this lesson in the “space and graphics ” module teaching methods and optimization strategies of some inspiration.