九年级学生在学完圆心角、弧、弦、之间的关系时,有这样一个定理:在同圆或等圆中,相等的圆心角所对的弧相等,所对的弦相等.事实上所对的弦的弦心距也是相等的.由于课改,这一条已被删除.我在给学生上这一节内容时是这样讲的:在同圆或等圆中,圆心角、弧、弦、弦心距这四组量中只要有一组量相等,则其它的三组量必分别相等.我形象的称之为“四合一定理”.学生听起来既感兴趣,又容易接受,同时宜于记忆.此定理可以分解成以下四个小 When the ninth grader learns the relationship between the central angle, the arc, and the string, there is a theorem that in the same circle or equal circle, the equal central angle is equal to the arc, and the right string is equal. The chords of the right string are also equal in pitch. Since the curriculum reform, this item has been deleted. I said this to the students in this section: In the same circle or equal circle, the angle of the circle, the arc, the string If there is a group of equal amounts in the four groups of strings, then the other three groups must be equal. My image is called “quadruple ”. Students are both interested and easy to accept. At the same time suitable for memory. This theorem can be broken down into the following four small