题目

They often stay at home and do their homework _______ weekends. A . in B . of C . for D . at 答案：D（2008•增城市模拟）如图，已知∠A0B=45°，P是∠A0B内一点，PO=22．（1）分别作点P关于OA、0B的对称点P1、P2；（尺规组图，不要求写作法，但要保留作图痕迹．）（2）求线段P1P2的长度．