日韩亚洲一区中文字幕,日韩欧美三级中文字幕在线,国产伦精品一区二区三区,免费在线欧美性爱链接

1.構(gòu)成: have / has been doing

3.現(xiàn)在完成時(shí)與一般過(guò)去時(shí)的區(qū)別:

①.現(xiàn)在完成時(shí)和一般過(guò)去時(shí)所表示的動(dòng)作都發(fā)生在過(guò)去, 但前者將過(guò)去的動(dòng)作與現(xiàn)在的結(jié)果或?qū)ΜF(xiàn)在的影響聯(lián)系起來(lái), 而后者只限于表示過(guò)去的動(dòng)作本身, 與現(xiàn)在無(wú)關(guān)

②.現(xiàn)在完成時(shí)不能與表明確時(shí)間的狀語(yǔ)如: yesterday, last year, two days ago, when I came in等連用, 但可與表示不明確時(shí)間的狀語(yǔ)如: already, yet, sometimes, often, before, lately, recently, once, twice, ever等連用, 也可以和包括現(xiàn)在在內(nèi)的時(shí)間狀語(yǔ)如: this morning, today, this week, this year等連用

　　　　 a. She has already come.

　　　　 b. I have met him before.

　　　　 c. Ma Hong has always been a good student.

　　　　 d. Have you ever been to the Great Wall ?

　　　　 e. I have seen him this morning.

2.用法:

①.表示動(dòng)作在說(shuō)話(huà)之前己經(jīng)完成, 而后果或影響至今仍存在

　　　　 a. He has gone to Shanghai. ( =He went to Shanghai and he is not here now. )

　　　　 b. I have opened the window. ( =I opened the window and the window is now open.)

　　　　 c. The concert has started. ( =The concert started and is now going on. )

　　　　 d. I have had breakfast. (=I had breakfast and I am not hungry now. )

　　 ②.表示開(kāi)始于過(guò)去, 持續(xù)到現(xiàn)在(也許還會(huì)繼續(xù)進(jìn)行下去)的動(dòng)作或狀態(tài), 用于延續(xù)性動(dòng)詞, 且句中常帶有表示段時(shí)間的時(shí)間狀語(yǔ)

　　　　 a. I have studied English since 1987.

　　　　 b. He has lived here for two years.

　　　　 c. He has been ill for ten days.

1.構(gòu)成: have / has done

2.用法:

　 　①.表示說(shuō)話(huà)時(shí)正在進(jìn)行著的動(dòng)作, 或現(xiàn)階段正在進(jìn)行而說(shuō)話(huà)時(shí)不一定正在進(jìn)行的動(dòng)作

　　　 　　a. I am writing a letter.

　　　 　　b. My mother is making a dress these few days.

　 �、�.表示即將發(fā)生的動(dòng)作(如在最近按計(jì)劃或安排好要進(jìn)行的動(dòng)作), 常見(jiàn)的有這種用法的動(dòng)詞有: come /go / leave / start / arrive等, 常與表示將來(lái)時(shí)間的狀語(yǔ)連用

　　　 　　a. They are going to Shanghai on Friday.

　　　 　　b. John is coming here next week.

　 　③.現(xiàn)在進(jìn)行時(shí)動(dòng)詞與always, continually, constantly等連用, 表示反復(fù)出現(xiàn)的或習(xí)慣性的動(dòng)作

　　　 　　a. The little boy is always asking questions.

　　　 　　b. You are always saying that sort of thing.

　 　④.在一定的上下文中, 前一句用一般現(xiàn)在時(shí)動(dòng)詞表述現(xiàn)在發(fā)生的事實(shí), 后一句用現(xiàn)在進(jìn)行時(shí)動(dòng)詞來(lái)闡述這一事實(shí)的原因, 結(jié)果, 目的等

　　　 　　a. He frowns. He is worrying about his boy.他皺著眉頭, 因?yàn)樗�在為他的孩子�?dān)心. (is worrying表示原因)

　　　 　　b. She criticizes him. She is trying to correct his wrong habits. 她批評(píng)他, 想糾正他的壞習(xí)慣. (is trying表示目的)

　　　 　　c. She lets her child have his own way. She is spoiling him. 她不管她的孩子, 把他慣壞了. ( is spoiling表示結(jié)果)

　 �、�.不表示持續(xù)的行為, 而表示知覺(jué), 感覺(jué), 看法, 認(rèn)識(shí), 感情, 愿望或某種狀態(tài)的動(dòng)詞通常不用現(xiàn)在進(jìn)行時(shí), 如: see, hear, smell, taste, recognize, notice, forget, remember, understand, know, believe, suppose, mean, think, love, hate, care, like, dislike, worry, forgive, want, wish, hope, refuse, feel like, belong to , possess, own, have, be, seem等

1.構(gòu)成: am / is / are doing

2.用法:

　 �、�.表示現(xiàn)狀, 性質(zhì), 狀態(tài), 經(jīng)常的或習(xí)慣性的動(dòng)作

　　　 　　a. It is fine today.

　　　 　　b. I am a student.

　　　 　　c. I get up at six every day.

d. My father never takes a bus; he walks to his office.

　 �、�.表示客觀事實(shí)或普遍真理

　　　 　　a. Japan is to the east of China.

　　　 　　b. The sun rises in the east.

　　　 　　c. A horse is a useful animal.

　 �、�.表示將來(lái)確定會(huì)發(fā)生的動(dòng)作(如己安排好或計(jì)劃好的動(dòng)作或按時(shí)刻表將來(lái)一定會(huì)發(fā)生的動(dòng)作), 可以這樣使用的動(dòng)詞有: go, come, leave, start, arrive等

　　　 　　a. My train leaves at 6:30.

　　　 　　b. The football match is played the day after tomorrow.

　 　④.在時(shí)間和條件狀語(yǔ)從句中可用一般現(xiàn)在時(shí)動(dòng)詞代替一般將來(lái)時(shí)動(dòng)詞

　　　 　　a. I will let you know as soon as I hear from him.

　　　 　　b. We will go if it is fine tomorrow.

　　　 　　c. I will be away when he arrives.

　　　 　　d. We shall not begin the discussion until he arrives.

　　　 　　e. Mother, I won’t go out unless you agree.

　　　 　　f. Don’t try to run before you begin to walk.

　 �、�.在某些以here / there開(kāi)頭的句子中用一般現(xiàn)在時(shí)動(dòng)詞表示現(xiàn)在正在發(fā)生的動(dòng)作

　　　 　　a. Here comes the bus.=The bus is coming.

　　　 　　b. There goes the bell.

　 　⑥.在體育比賽過(guò)程中, 解說(shuō)員敘述迅速, 短暫動(dòng)作時(shí), 可用一般現(xiàn)在時(shí), 表示正在進(jìn)行的或剛剛發(fā)生的動(dòng)作

　　　 　　a. Ma Lianbao passes the ball to Mu Tiezhu, Mu shoots – a fine shot !

　 �、�.在劇本或圖片的說(shuō)明文字中, 用一般現(xiàn)在時(shí)表示動(dòng)作

　　　 　　a. When the curtain rises, Juliet is sitting at her desk. The phone rings. She picks it up and listens quietly.

1.構(gòu)成: 通常以動(dòng)詞原形表示. 主語(yǔ)為第三人稱(chēng)單數(shù)時(shí), 則用動(dòng)詞的第三人稱(chēng)單數(shù)形式來(lái)表示

8.已知

(1)　　 若x∈R，求f(x)的單調(diào)遞增區(qū)間；

(2)　　 若時(shí)，f(x)的最大值為4，求的值

[解](1)由

使

,解得,

(2)由f(x),因此f(x)在上的最大值為+3，使+3=4,　 =1.

6.化簡(jiǎn)

并求函數(shù)的值域和最小正周期和遞增區(qū)間.

解：

所以函數(shù)f(x)的值域?yàn)?sub>，最小正周期

由.(k∈Z)

(2006上海) 求函數(shù)的值域和最小正周期.

[解] 　

　∴ 函數(shù)的值域是,最小正周期是；

(2005重慶卷)若函數(shù)的最大值為，試確定常數(shù)a的值.

解：

因?yàn)?sub>的最大值為的最大值為1，則

所以