“角的分类”是人教版四年级数学上册第二单元的教学内容。结合预备知识——角的度量,学生在本节课上将深化对直角、锐角和钝角的认识,并且进一步认识两种新的角——平角和周角。下面是该课的一段教学实录:教师在黑板上画了一个周角。师:同学们,这个角你们见过吗?生齐答:见过。生1:我知道,这个角叫周角。师:你真聪明,连它的名字你也知道。没错,它就 “Corner classification ” is the teaching content of the second unit of the fourth edition of the PEP. In combination with the preliminary knowledge-measure of angles, students will deepen their understanding of right angles, acute angles and obtuse angles in this lesson, and further understand two new angles, the flat angle and the circumferential angle. The following is a lesson record of the lesson: The teacher draws a corner on the blackboard. Teacher: Classmates, have you ever seen this corner? Health 1: I know that this corner is called Zhou corner. Teacher: You're so smart, you know, even its name. That's right, it's