如图，AB切⊙O于点B，OA=5√5，tanA=1/2，弦BC∥OA

(1)求AB的长

(2)求四边形AOCB的面积.

---HowwasyourvacationinShanghai?

---Oh,__________,Ican’tstandit.Thereweretoomanypeopleandtheweatherwastoohot.

了却君王天下事，__________。(辛弃疾《破阵子》)

下列变化，一定发生了化学变化的是()

Thepatient'sprogresswasencouraging,ashecould_______getoutofbedwithout