《锐角、钝角》教学片断一师:现在四人小组合作,把画好的角放在一起,看一看:角的大小;想一想:可分几类?分一分。(学生四人小组合作、分类)师:哪一组来汇报?生1:我们组把角分成了三类,一类比直角大,一类是直角,还有一类比直角小。师:先看比直角小的角(逐一出示),比直角小吗?(学生逐一判断)有比较难判断的吗? “Acute angle, obtuse angle” teaching piece a Division: Now four team work together to draw a good corner, take a look: the size of the corner; Think about it: can be divided into several categories? Teacher: Which group to report? Health 1: Our group into the angle into three categories, one is larger than the right angle, one is a right angle, there is a smaller than the right angle. Teacher: Look at the angle than the small angle (one by one show), smaller than the right angle? (Students one by one judge) is more difficult to judge it?