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一、创设情境,因势利导思维是由问题引起的,教师一开始就创设问题的情境,调动学生的学习兴趣。首先,让学生辨认几个等圆中的扇形(如图1—4),提问:“这四个等圆中扇形面积有的大、有的小,它们是随着什么变化的?”然后让学生辨认两个圆心角相同的扇形(如图5—6),提问:“这两个圆心角相等的扇形面积有的大、有的小,它们又是随着什么变化的?”通过上面两问,使学生初步了解扇形面积的大小与“圆心角”和“半径”有关,为分散教学难点打下基础。最后,教师再让学生想一想,扇形面积怎样计算呢?(揭示课题)
First, create a situation, the best of the best is caused by the problem of thinking, the teacher from the very beginning to create a problem situation, to mobilize students' interest in learning. First, ask the students to identify the sectors in several circles (Figure 1-4) and ask, “What are the sizes of the sectors in the four circles, and how small are they changing?” Students identify two sectors of the same central angle (Figure 5-6), ask: “The two central angle equal to the fan-shaped area some big, some small, which is with them what change?” Through the above two Ask, enable students to initially understand the size of the fan-shaped area and the “central angle” and “radius” related to lay the foundation for the dispersion of teaching difficulties. Finally, teachers let the students think again, how to calculate the sector area? (Reveal the subject)