题目

已知菱形中，，，沿对角线将折起，使二面角为，则点到所在平面的距离等于 ． 答案：【答案】【解析】设AC与BD交于点O．在三角形ABD中，因为∠A＝120°，AB＝2．可得AO＝1．过A作面BCD的垂线，垂足E，则AE即为所求．由题得，∠AOE＝180°−∠AOC＝180°−120°＝60°．在RT△AOE中，AE＝AO•sin∠AOE＝．用括号内所给中文写出正确的单词1.There are many ________ (工厂) along the river, so the pollution is serious.2.We should try our best to protect our __________ ( 环境).3.During the Spring Festival children always get red pockets from their parents and ________(亲戚).4.On my last birthday, I ________ (收到) a lot of presents from my friends.5.There are many interesting _____ (节目) on TV and I can have a good time watching them at weekends.