6．如图是跷跷板的示意图，支柱OC与地面垂直，

点O是横板AB的中点，AB可以绕着点O上下转动，

当A端落地时，∠OAC=20°，则横板AB上下可转动

的最大角度(即∠A′OA)是 　　　　度 。

5．计算　=　　　　　 　。

4．如图正方形的边长为4cm，则图中阴影部分

的面积为　　　 cm²．

3．如图在Rt△ABC中，∠C=90°∠B=30°，AB=2，

　 则AC=　　 。

2．=　　　　 　。

1．在实数 ，，　 　， ， 　中是　　　　　 无理数 。

20. She was often heard to say that she _______ (厌倦了) her work. So it came as no surprise when Sarah announced that she was to leave office soon. (enough)

19. The Group of Eight ________ (由……组成) the eight richest countries in the world. ( consist) 教育博客

18. The film I saw yesterday ________ (让我回想起了我度过的那些日子) with my best friend in Paris. (remind) 教育博客

17. Everything should ________ (摆放地有条有理) so that it is always at hand whenever we need it. (organize)