题目

如图，在△ABO中，AB⊥OB，OB＝，AB＝1.将△ABO绕O点旋转90°后得到△A1B1O，则点A1的坐标为________． 答案：(－1，)或(1，－)根据句意, 用所给单词的适当形式填空。【1】There are many beautiful ________ (beach)in Dalian.【2】Chemicals are ______(harm) to the environment.【3】My parents _______(been) to Shanghai twice.【4】Joan can’t run as _____________ (quick) as Alice.【5】Lots of mistakes________(make) by him.