题目

边长为2的两种正方形卡片如图①所示，卡片中的扇形半径均为2．图②是交替摆放A、B两种卡片得到的图案．若摆放这个图案共用两种卡片21张，则这个图案中阴影部分图形的面积和为      （结果保留π）． 答案：解析:略—I hear the beginning of this movie is very exciting.— ! When I got to the cinema yesterday, the film had been on for several minutes.A. It’s a pleasure B. I’m sorry to hear that. C. What a pity