题目

正方体， （1）求证：平面； （2）求直线与平面所成角正弦值. 答案：解：(Ⅰ)∵ ∴，而 ∴，同理， 而、为平面上相交两直线， ∴ (Ⅱ)以分别为轴建立空间直角坐标系，不妨设正方体棱长为1， 则有，，， 由(Ⅰ)知平面的一个法向量为， 而， ∴， ∴直线所成角的正弦值为．Complete the following sentences as required (根据所给要求，完成下列句子。每空格限填一词) (共14分)1.Anna goes to the school library twice a week. (改为一般疑问句)________ Anna ________ to the school library twice a week?2.They went to the supermarket to buy some food for the picnic yesterday.(对划线部分提问)________ ________ they go to the supermarket yesterday?3.Students mustn’t smoke because smoking is harmful to their health. (保持句意基本不变)Students ________ ________ to smoke because smoking is harmful to their health.4.“Have you finished reading the report?” the manager asked me. (合成宾语从句)The manager asked me ________ I ________ finished reading the report.5.The old man has planted many trees since he came to live here.（改为被动语态）Many trees ________ ________ planted by the old man since he came to live here.6.It’s fun to go for a spring outing with my classmates.(改为感叹句)________ ________ it is to go for a spring outing with my classmates!7.foot, had, you, better, on, there, go (连词成句)___________________________________________________________________.