17．····························································································································································· 下列条件中，能说明四边形ABCD是平行四边形的是·························································································································· (　 　)．

　　 (A)∠A＝30°，∠B＝150°，∠C＝30°，∠D＝150°

　　 (B)∠A＝60°，∠B＝60°，∠C＝120°，∠D＝120°

　　 (C)∠A＝60°，∠B＝90°，∠C＝60°，∠D＝150°

　　 (D)∠A＝60°，∠B＝70°，∠C＝110°，∠D＝120°

16．某数的平方根等于它的立方根，则这个数··································································· ( 　　)．

　　 (A)1　　　　　　　　　　 (B)－1　　　　　　　　　 (C)0　　　　　　　　　　 (D)以上都不对

15．····························································································································································· 在4，3.5，π，，五个数中，无理数有·············································································································································· (　 　)．

　　 (A)1个　　　　　　　　 (B)2个　　　　　　　　 (C)3个　　　　　　　　 (D)4个

14．····························································································································································· 用刻度尺分别画下列图形的对称轴可以不用刻度尺上的刻度画的是···························································································· ( 　　)．

　　 (A)①④　　　　　　　　 (B)②③　　　　　　　　 (C)③④　　　　　　　　 (D)①②

13．····························································································································································· 下列各数组中，不是勾股数的是····························································································································································· ( 　　)．

　　 (A)5，12，13　　　　　　　　　　　　　　　　　　　　 (B)7，24，25　　　

　　 (C)8，12，15　　　　　　　　　　　　　　　　　　　　 (D)3k，4k，5k(k为正整数)

12．····························································································································································· 的平方根是　　　 (　 　)．

　　 (A)±12　　　　　　　　 (B)12　　　　　　　　　　 (C)－12　　　　　　　　 (D)±

11．近似数2.023的有效数字是···································································································· (　 　)．

　　 (A)1个　　　　　　　　 (B)2个　　　　　　　　 (C)3个　　　　　　　　 (D)4个

10．如图，△ABC是等腰直角三角形，D是斜边BC上的中点，

△ABD绕点A旋转到△ACE的位置，恰好与△ACD组成正方

形ADCE，则△ABD按　　 时针方向旋转了　　　　　 ．

9．如图，等腰梯形ABCD中，AD∥BC，AD＝3，AB＝6，BC＝8.

且DE∥AB，则△DEC的周长是　　　　　 ．

8．如图，在△ABC中，∠C＝90°，AD平分∠BAC，若

CD＝6 cm，则点D到AB的距离是　　　　　 　cm．