题目

（本小题13分）已知函数 （1）用五点法画出它在一个周期 内的闭区间上的图象； （2）指出的周期、 振幅、初相、对称轴； （3）说明此函数图象可由 上的图象经 怎样的变换得到. 答案：（1）略  （2）略  （2）略 x 0 y36303 解析:（1）列表 (2)周期T＝，振幅A＝3，初相， 由， 得即为对称轴； （3）①由的图象上各点向左 平移个长度单位，得的图象； ②由的图象上各点的横坐 标伸长为原来的2倍（纵坐标不变），得的图象；③由的图象上各点的纵坐标伸长为原来的3倍（横坐标不变），Life in the 2100s will be very different from life today. Between then and now many changes will take place. What will the changes be?The population is growing fast. There will be more people in the world and most of them will live longer than people do now.Computers will be much smaller and more useful, and there will be at least one in every home. And computer studies will be one of the important subjects in schools then.People will work fewer hours than they do now and they will have more free time for sports, watching TV and traveling. Traveling will be much easier and cheaper. More people will go to other countries on holiday.There will be changes in our food, too. Maybe no one will eat meat every day. Instead, they eat more fruit and vegetables. Maybe people will be healthier.Work in the future will be different, too. Dangerous and hard work canl be done by robots, because of this, many people will not have work to do. This will be a problem.1.There will be in the future.A. small population B.few changesC. more people D. few vegetables2.In the future the computer will be .A. much bigger and few people will use itB. much smaller and more usefulC. smaller and not many people will use itD. bigger and a lot of people will use it3.In the future more people .A.will go to other countries for holidaysB. will study at schoolC. will go to work earlierD.will work for many hours4.People will prefer to in the future.A. fruit and vegetables; meatB.meat; fruit and vegetablesC. fruit and meat; vegetablesD.meat and vegetables; fruit5.The robots will in the future.A. do the dangerous workB.do all the workC. do only houseworkD.do the easy work for people