题目

情景交际A: Hello, Betty. B: Hello, Tony. Our classroom is reallybig. There are 46 students in my class. A: There are 45 students in my class.B: A: Yes, there are two maps on the wall, amap of the world and a map of China,B: A: No, there isn't a TV in my classroom.But there is a computer.B: A: It's on the teacher's desk. Oh, it'stime for class(该上课了). Bye.B: Bye. 答案：【1】What's your classroom like?【2】How many students are there in your class?【3】Are there any maps on the wall?【4】Is there a TV in your classroom?【5】Where is it/ the computer? 在三棱锥P－ABC中，AC＝a，BC＝2a，AB＝a，侧棱PA、PB、PC与底面ABC所成的角相等，点P到平面ABC的距离为． (Ⅰ)求二面角P－AC－B的大小； (Ⅱ)求点B到平面PAC的距离．