题目

如图，在矩形ABCD中，AB=4，BC=3，E为DC边的中点，沿AE将△ADE折起，使二面角D﹣AE﹣B为60°，则直线AD与面ABCE所成角的正弦值为 ． 答案：考点： 直线与平面所成的角． 专题： 证明题；综合题；压轴题． 分析： 作DO垂直面ABCD，垂足为O，过O作OF垂直AE于F，连接DF、OA，则∠OFD为二面角D﹣AE﹣B的平面角等于60°，∠OAD为直线AD与面ABCD所成角，解三角形OFD，和三角形OAD，即可求出直线AD与面ABCE所成角的正弦值． 解答： 解：作DO垂直面ABCD，垂 Why did Marco Polo come to China? [　　] A．He liked traveling and he traveled to China． B．He came with his father who was doing business． C．He came to China specially to visit the Emperor． D．He came to write his books．