深圳市龙华新区开展研讨课活动,笔者有幸担任数学科执教者之一。按照教学进度,笔者选择了北师大版小学数学四年级下册探索与发现(二)《三角形边的关系》一课。本课是在学生初步认识了三角形,知道三角形有三个顶点、三条边、三个角以及具有稳定性的基础上进行学习的。在教材的编排上,本课分为三部分:一是呈现了四组小棒,让学生在摆一摆的过程中,发现哪组小棒可以围成三角形,哪组小棒不能围成三角形。二是把摆一摆的实验数据(小棒的长度)填入表内,为学生发现三角形边的关系创造条件。三是通过学生的讨论,在数据的比较中发现三角形三条边的关系。为了打破常规的设计思路,体现“用教材”的思 Longhua New District, Shenzhen seminar activities, I was fortunate to serve as one of mathematics coaching. In accordance with the teaching progress, I chose the North Normal University Primary School mathematics grade four volumes of exploration and discovery (b) “triangle side of the relationship” a lesson. This lesson is based on a preliminary understanding of the triangle by a student, knowing that the triangle has three vertices, three sides, three corners, and stability. In the textbook layout, the lesson is divided into three parts: First, there are four groups presented a small stick, so that students in the process of posing, which group of small sticks can be formed into a triangle, which group of small sticks can not form a triangle . The second is to put the experimental data (stick length) fill the table, to create the conditions for students to find the triangle side of the relationship. Third, through the students’ discussions, we found the relationship between the three sides of the triangle in the data comparison. In order to break the conventional design ideas, reflect the “textbook” thinking