案例1:一节数学公开课,教师执教人教版小学数学12册《圆柱的认识》。在教学进程中巩固练习阶段,教师引导学生完成书上练习:指出下面图形中哪些是圆柱。(1)(2)(3)(4)学生根据直圆柱的定义,将(2)(4)判断成圆柱。此时,有学生举手问:“老师,(1)(3)我经常见到,它们既然不是圆柱,哪是 Case 1: A Mathematical Open Class, Teachers Teach PEP Primary School Mathematics 12 volumes “Understanding of the Cylinder.” In the process of teaching to consolidate the practice phase, the teacher guides the students to complete the book practice: pointing out which of the following figures are cylindrical. (1) (2) (3) (4) The student judges (2) (4) as a cylinder according to the definition of a straight cylinder. At this moment, some students raise their hands and ask: "Teacher, (1) (3) I often see that since they are not cylindrical, which is