数学活动小组为测量山顶电视塔的高度，在塔的椭圆平台遥控无人机．当无人机飞到点P处时，与平台中心O点的水平距离为15米，测得塔顶A点的仰角为30°，塔底B点的俯角为60°，则电视塔的高度为_________米．
20√3
—This is really a wonderful party with interesting people and great food.
—I’m glad you are _____.
—Would you like ___ some fruit?
—No thanks. I don’t feel like _____ anything now.
—He seems _____ ill. Shall we take him to the hospital right now?
—I don’t think it matters. Maybe he’s caught a bit of a cold.
—The rain came to a stop the night before. The fields are still full of water.
—It _____ for nearly a week.
—I think he lives _____ No.386 West St.
—Are you sure _____ that? You’d better make sure.
—How long ____ you ____a fever?
—Ever since last night.
—The artist has got _____ much work to do that he hardly has time to help his wife with the housework.
—That’s true. Even on Sundays he is busy with his work.
—What do you think of these two books?
—_____ of them are interesting. And I’ve read them several times.
—My trousers are______ .
—I’ll buy you a new pair.
—Will you please show me how to operate the new machine?
—Sure. It’s a piece of cake. Now let me tell you _____ to do first.
