题目

如图,在正方体ABCD﹣A1B1C1D1中,直线A1C与平面ABCD所成角的余弦值是（ ）A. B. C. D. 答案：【答案】D【解析】连接,根据线面角定义可以判断出是直线A1C与平面ABCD所成角,设出正方体的棱长,利用勾股定理和锐角的三角函数定义可以求出直线A1C与平面ABCD所成角的余弦值.连接,由正方体的性质可知：A1A平面ABCD,由线面角的定义可知：是直线A1C与平面ABCD所成角,设正方体的棱长为1,底面是与正方形,故,写作（满分30分）得分评卷人   近几年，某些旅行社组织中学生在寒暑假期间赴著名大学旅游，人们对此褒贬不一。请用英语写一篇论说文，介绍问题； 2.讨论利弊；3.表明自己的观点。字数：120-150。参考词汇：旅行社travel agency    校园  campus ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________