案例背景:图形与几何是小学数学四大领域内容之一,其教学目标之一就是促进学生空间观念的发展。如何结合学生的心理特征,立足并用好学生经验,处理好直观和抽象的关系,有效发展学生空间观念?这一问题一直是数学教师关注的热点。带着这些思考,笔者尝试着执教四年级下册《等腰三角形和等边三角形》一课。片段一师:前面我们已经研究了三角形,请大家回顾一下,三角形按角分类,可以分成几类?生:三角形按角可以分成直角三 Case Background: Graphics and Geometry are one of the four major areas of elementary mathematics. One of the aims of teaching is to promote the development of students’ space concepts. How to combine the psychological characteristics of students, based on and make good use of student experience, to deal with the relationship between visual and abstract, and effectively develop the concept of student space? This issue has been the focus of mathematics teachers. With these thoughts, I try to teach the fourth grade volume “isosceles triangle and equilateral triangle” class. Fragment of a division: In front of us have studied the triangle, please review, the triangle by angle classification, can be divided into several categories: Health: triangle by angle can be divided into three