笔者研究2015年常州市数学中考题的第18题时,感觉学生不好下手,不容易寻找到解题思路及其突破点,同时发现命题老师给出的答案同样是学生不容易想到的,而且也不是最简捷的.题目:如图1,在⊙O的内接四边形ABCD中,AB=3,AD=5,∠BADD=60°,点C为弧BD的中点,则AC的长是____.为了研究方便,先呈现命题老师提供的标准答案.解:分别过C作CE⊥AB于 When I study the 18th essay of the Changzhou math test in 2015, I feel that it is not easy for students to find a solution to the problem and their breakthrough points. At the same time, I find that the answer given by the proposition teacher is also hard to think by the students, Is not the most simple Title: As shown in Figure 1, in the ⊙ O of the inscribed quadrilateral ABCD, AB = 3, AD = 5, ∠ BADD = 60 °, point C is the midpoint of the arc BD, AC is long ____. In order to facilitate the study, first presented the standard answer provided by proposition teacher. Solution: C for CE ⊥ AB