题目

如图,水坝的横断面是梯形,背水坡AB的坡角∠BAD=,坡长AB=,为加强水坝强度,将坝底从A处向后水平延伸到F处,使新的背水坡的坡角∠F=,求AF的长度(结果精确到1米,参考数据: ,)   答案：解：过B作BE⊥AD于E  在Rt△ABE中，∠BAE=60°，∴∠ABE=30° ∴AE= AB                                   --------2分 ∴BE=     --   -----2分 ∴在Rt△BEF中，∠F=45°， ∴EF=BE=30 ∴AF=EF-AE=30- -------------------------------2分 ∵  ∴AF=12.68≈13。------2分The house rent is expensive. I’ve got about half the space I had at home but I have to pay_______here. A. as three times much            B. as much three times C. much as three times            D. three times as much