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人教版高中生物必修2DNA的復制說課稿

  • 新人教版高中英語必修1Unit 1 Teenage Life-Listening and Speaking & Listening and Talking教案

    新人教版高中英語必修1Unit 1 Teenage Life-Listening and Speaking & Listening and Talking教案

    Step 2 Listening and Talking1. The teacher is advised to talk with their new students about the related topic: Boys and girls, do you know some structures to talk about future activities? Talking about future activitiesWe’ll …I plan to …There’ll be …I hope to …We’re going to …2. After their small talk, the teacher can move on by playing the listening and solve the following task.Underline the expressions in the sentences below Cao Jing and Max use to talk about the future.We’ll learn useful skills.I plan to improve my spoken English.There’ll be students from different schools.I hope to make new friends.We’ll talk about teenage life.I’ll learn to make a fire.There’ll be students from different countries at the camp.There’ll be some experts there to show us how to live in the wild.We’re going to learn about wildlife.I’m going to give a speech.I think I’m going to enjoy the activities.I think we’ll have a lot of fun.3. Work in groups. Plan a youth camp.Teacher make the Ss think of ideas for the camp. And they can use the questions below to get started. And have the Ss present their ideas for a youth camp to the class.●What kind of camp is it?●Who will be there?●What will they do?●What will they learn?

  • 新人教版高中英語必修1Unit 3 Sports and Fitness-Listening and Speaking & Listening and Talking教案

    新人教版高中英語必修1Unit 3 Sports and Fitness-Listening and Speaking & Listening and Talking教案

    Finally, after finishing the task above, the teacher is expected to instruct students to work in groups to finish the following project:Speaking ProjectWhat event or activity would you like to invite your friend to? Make a conversation with a partner.Ski Race: Zhangjiakou, a beautiful city in northern China, will host the Youth Ski Race in December.Track Meet: a great event for track –and –field lovers on 26 October.Gym Class: come and work out at a gym! You can make it.Part 2: Listening and Talking:The teacher is advised to talk with their new students about the related topic: Boys and girls , what do you think of sportsmanship? Let’s listen and find out:Play the listening and match each opinion with the right speaker. Who do you agree with? Why?Cao Jing _____________ Lily _____________ Max _____________A. An athlete should do his/her best to win.B. The girl should stop and help the other girl. Good sportsmanship is more important than wining!C. An athlete should think about honor and his/her fans if he/she is competing for his/her country.Listen again and circle the expressions that you hear in the conversation.

  • 新人教版高中英語必修1Unit 3 Sports and Fitness- Discovering Useful Structures—tag questions教案

    新人教版高中英語必修1Unit 3 Sports and Fitness- Discovering Useful Structures—tag questions教案

    【教材分析】This teaching period mainly deals with the grammar: tag questions.This period carries a considerable significance to the cultivation of students’ spoken English. The teacher is expected to enable students to master this period thoroughly and consolidate the knowledge by doing some exercise of good quality.【教學目標與核心素養(yǎng)】1. Get students to have a good understanding of the basic usages of tag questions.2. Enable students to use the basic phrases structures flexibly.3. Develop students’ speaking and cooperating abilities.4. Strengthen students’ great interest in grammar learning.【教學重難點】1. How to enable students to have a good understanding of the basic usages of tag questions.2. How to enable students to use the basic usages of tag questions flexibly.【教學過程】Step1: 語法自主探究一、基本組成方法1.肯定式陳述部分+否定附加疑問部分(前肯后否) You often play badminton, don’t you? 你經常打羽毛球,是嗎?You are going to the gym with me, aren’t you?你要和我一起去健身房,是嗎?She’s been to shanghai before, hasn’t she? 她以前去過上海,是嗎?2.否定式陳述部分+肯定附加疑問部分(前否后肯) It isn't a beautiful flower, is it? 那不是美麗的花,是嗎?You didn't go skating yesterday, did you? 你昨天沒去滑冰,是嗎?They can’t finish it by Friday, can they?他們不能在星期五之前完成,是嗎?

  • 新人教版高中英語必修3Unit 1 Festivals and Celebrations-Reading and Thinking教學設計

    新人教版高中英語必修3Unit 1 Festivals and Celebrations-Reading and Thinking教學設計

    The topic of this part is “Discover the reasons for festivals and celebrations.The Listening & Speaking & Talking part aims at talking about the experiences and feelings or emotions about the festivals and celebrations. This section aims at detecting the reason why the people celebrate the festivals, the time, the places, the types and the way of celebrations. It also explains why some traditions in the old celebrations are disappearing, like the firecrackers in the big cities and some new things are appearing like the prosperity of business or commerce. 1. Students can talk about what festivals they know and the reasons and the way of celebrating them.2. Students should learn the reading skills such as the headline and get the topic sentences, the structures of articles.3. Students can understand the past, the present situation of some festival around the world and why there are some changes about them. 4. Students can have the international awareness about the festivals.1. Students should learn the reading skills such as the headline and get the topic sentences, the structures of articles.2. Students can understand the past, the present situation of some festival around the world and why there are some changes about them.Step 1 Lead in---Small talkWhat festival do you like best ? Why ?I like the Spring Festivals because I can set off the fireworks, receive the lucky money and enjoy the Gala with my families.Step 2 Before reading---Pair workWhy do people celebrate different festivals ?The Spring Festivals is to celebrate the end of winter and the coming of spring and new life.The Mid-autumn Day is to celebrate the harvest and admire the moon.

  • 新人教版高中英語必修3Unit 4 Space Exploration-Reading and Thinking教學設計二

    新人教版高中英語必修3Unit 4 Space Exploration-Reading and Thinking教學設計二

    The theme of this unit focuses on “space exploration.” Students will learn about the training and experience needed to become an astronaut. The text is mainly about the development of space exploration. On the one hand, the text helps students to have a good understanding about the great feats humans have achieved, on the other hand, they will further understand the contributions that we Chinese have achieved, and feel confident and proud about our homeland and strengthen their love for our country. The teacher should instruct students to aim high and study harder to make great progress in the space career if possible.1. Read about the development and value of space exploration.2. Explore the mysteries of the universe and the achievements in space exploration.3. Skillfully use the vocabulary of this text to cultivate self-study ability 4. Develop cooperative learning ability through discussion.1. Enable the Ss to talk about the development and value of space exploration.2. Guide the Ss to summarize the main idea of each paragraph as well as the main idea of the text.3. Help Ss comprehend the main reasons for space exploration. Multi-media, textbook, notebooks.Step 1: Warming up and predictionLook at the title and the pictures of the text and predict what the text will be about?2. What are the main reasons for space exploration?

  • 新人教版高中英語必修3Unit 5 The Value of Money-Listening &Speaking教學設計

    新人教版高中英語必修3Unit 5 The Value of Money-Listening &Speaking教學設計

    Step 4: Listen again and decide if the following statements are true (T) or false (F).1 It was the first time Chen Liyan's story was reported. T口 F口2 Chen found 10,000 yuan in a small plastic bag in Taiyuan railway station口 F口3 Wang Zheng apologized to Chen because he couldn't offer her more money. T口 F口4 Chen took out a large loan to cure her daughter, T口 F口5 Wang set up a fundraising website for Chen's daughter after Chen told him about her situation. T口 F口Step 5:After listening, discuss the questions.1 What kind of person do you think Chen Liyan is?Chen Liyan is generous and honest because she returned a large sum of money to the owner.2 Did Chen return the money because she didn't need it?No. She returned the money because it was the right thing to do. Evidence for this is that she refused to accept the reward money because she felt that it had not been earned. 3 Is it common for people to do what Chen did?It depends on the culture. In some countries it is quite common to return money that has been found. In other countries, people believe "Finders are keepers!" 4 How did Wang Zheng feel about the return of his money?He must have been very happy and relieved to have gotten his money back. We know this because he thanked Chen repeatedly and even offered her a reward.5 Why did Ma Dongbao tell Wang about Chen's family?He must have had great sympathy for Chen and her daughter and wanted to help them.'We know this because he arranged help for them. 6 How did the news reporter feel about Chen's actions?The news reporter felt that it showed that money wasn't the most important thing in life. We know this because the reporter told us that this is what Chen believes. and then said, “that's a great attitude to take."

  • 人教版高中地理必修3第五章第二節(jié)產業(yè)轉移教案

    人教版高中地理必修3第五章第二節(jié)產業(yè)轉移教案

    1.閱讀圖5.16,說明產業(yè)向國外轉移對日本經濟的不利影響。點撥:圖5.16直觀的顯示了產業(yè)轉移對日本經濟的不利影響:形成“產業(yè)轉移出去的多,轉移進來的少→國內生產投資不足,生產困難→市場萎縮→產業(yè)向外轉移,外資不愿進入”的惡性循環(huán)。2.盡管重化工業(yè)的環(huán)境污染比較嚴重,但是卻能為工業(yè)化的發(fā)展提供堅實的基礎,因此成為發(fā)達工業(yè)的象征。日本、韓國的經濟發(fā)展都經歷了由輕工業(yè)(勞動密集型)到重化工業(yè)(資源密集型和資金密集型)到高科技工業(yè)(技術密集型)的階段。(1)為什么日本、韓國在重點發(fā)展重化工業(yè)之前,要先發(fā)展勞動密集型工業(yè)?點撥:重化工業(yè)的發(fā)展一方面需要有一定的工業(yè)基礎和技術工人,另一方面需要投入大量的資金,先發(fā)展勞動密集型工業(yè)有利于利用勞動力資源豐富且廉價的優(yōu)勢,積累資金和造就產業(yè)工人。所以,勞動力豐富的發(fā)展中國家或地區(qū)的工業(yè)化往往從優(yōu)先發(fā)展勞動密集型工業(yè)開始。

  • 新人教版高中英語必修3Unit 5 The Value of Money-Discovering Useful Structures導學案

    新人教版高中英語必修3Unit 5 The Value of Money-Discovering Useful Structures導學案

    4.They were going to find someone to take part in their bet when they saw Henry walking on the street outside.[歸納]1.過去將來時的基本構成和用法過去將來時由“would+動詞原形”構成,主要表示從過去某一時間來看將要發(fā)生的動作(尤其用于賓語從句中),還可以表示過去的動作習慣或傾向。Jeff knew he would be tired the next day.He promised that he would not open the letter until 2 o'clock.She said that she wouldn't do that again.2.表示過去將來時的其他表達法(1)was/were going to+動詞原形:該結構有兩個主要用法,一是表示過去的打算,二是表示在過去看來有跡象表明將要發(fā)生某事。I thought it was going to rain.(2)was/were to+動詞原形:主要表示過去按計劃或安排要做的事情。She said she was to get married next month.(3)was/were about to+動詞原形:表示在過去看來即將要發(fā)生的動作,由于本身已含有“即將”的意味,所以不再與表示具體的將來時間狀語連用。I was about to go to bed when the phone rang.(4)was/were+現(xiàn)在分詞:表示在過去看來即將發(fā)生的動作,通??捎糜谠摻Y構中的動詞是come,go,leave,arrive,begin,start,stop,close,open,die,join,borrow,buy等瞬間動詞。Jack said he was leaving tomorrow.

  • 《故都的秋》《荷塘月色》《我與地壇》群文閱讀說課稿 2022-2023學年統(tǒng)編版高中語文必修上冊

    《故都的秋》《荷塘月色》《我與地壇》群文閱讀說課稿 2022-2023學年統(tǒng)編版高中語文必修上冊

    (2) 中國文人的悲秋情結。3.《荷塘月色》中,作者為什么要離開家來到荷塘散步?4. 思考:作者的心里為何“頗不寧靜?”(教師補充:寫作背景)5. 出門散步后,作者的心情發(fā)生變化了嗎? 有怎樣的變化?6.思考討論:為什么作者說“我”與“地壇”間有著宿命般的緣分,二者有何相似之處?(閱讀1-5段)7.思考:作者從他同病相憐的“朋友“身上理解了怎樣的”意圖“?三、課堂總結李白說:“天地者,萬物之逆旅也。”人生,如同一場旅行,在人生的旅途中,時而高山,時而峽谷,時而坦途,時而歧路。我們或放歌,或悲哭,然而,大自然始終以其不變的姿勢深情地看著我們,而我們,也應該學會在與自然的深情對望中,找到生命的契合。正如敬亭山之于李白,故都的秋之于郁達夫,荷塘月色之于朱自清,地壇之于史鐵生,他們從中或得到心靈的慰藉、精神的寄托,或得到生存的智慧與勇氣,最終完成精神的超脫。

  • 《一個消逝了的山村》說課稿  2021—2022學年統(tǒng)編版高中語文選擇性必修下冊

    《一個消逝了的山村》說課稿 2021—2022學年統(tǒng)編版高中語文選擇性必修下冊

    這幾段內容傳達出的是“要敬畏生命,尊重生命;更要敬畏大自然,尊重大自然,愛護大自然”的主旨內涵,因此讓學生通過自由朗讀的方式,再次體會馮至對這個消逝了的山村的細致的美好的描繪,感悟馮至傳達出的對生命,對自然的理解和思考。5.最后一個自然段的解讀依然是交給學生,先齊讀課文,再讓學生自主分享自己的體會或疑惑。但在這一環(huán)節(jié)我也設計了兩個我認為必須解答的兩個問題,一是怎么理解“在風雨如晦的時刻”;二是“意味不盡的關聯(lián)”是指什么。我認為這兩個問題一個涉及到寫作背景,一個涉及到對全文主旨的一個整體把握,能夠進一步幫助學生理解散文的深刻內涵和主旨,讓學生有意識的在閱讀散文過程中通過背景知識進行理解。既尊重學生的個性化解讀,又能夠讓學生有意義學習,完成預設的教學目標。如果學生沒有提到這兩處,那我就需要做出補充。

  • 人教版新課標高中地理必修2第四章第三節(jié)傳統(tǒng)工業(yè)區(qū)與新工業(yè)區(qū)教案

    人教版新課標高中地理必修2第四章第三節(jié)傳統(tǒng)工業(yè)區(qū)與新工業(yè)區(qū)教案

    知識目標1.了解傳統(tǒng)工業(yè)區(qū)的分布、條件和工業(yè)部門。2.掌握傳統(tǒng)的魯爾工業(yè)區(qū)優(yōu)越的區(qū)位條件,了解它的衰落原因及其綜合整治途徑。能力目標1.讀圖分析礦產資源與工業(yè)部門之間的聯(lián)系,培養(yǎng)學生的地理思維能力、綜合分析能力,明確工業(yè)生產也應因地制宜。2.聯(lián)系實際,了解當?shù)貍鹘y(tǒng)工業(yè)發(fā)展狀況,為適應當今世界經濟發(fā)展狀況,應有哪些改善措施,培養(yǎng)學生的創(chuàng)新能力。德育目標1.通過了解魯爾區(qū)的發(fā)展變化,用發(fā)展的觀點看待傳統(tǒng)工業(yè)區(qū)的改造,適應世界發(fā)展潮流。2.中國已經“入世”,我們應用辯證唯物主義觀點分析我國傳統(tǒng)工業(yè)今后遇到的機遇和挑戰(zhàn)。

  • 人教版新課標高中地理必修2第二章第一節(jié)城市內部空間結構教案

    人教版新課標高中地理必修2第二章第一節(jié)城市內部空間結構教案

    為城市居民提供休養(yǎng)生息的場所,是城市最基本的功能區(qū).城市中最為廣泛的土地利用方式就是住宅用地.一般住宅區(qū)占據(jù)城市空間的40%—60%。(閱讀圖2.3)請同學講解高級住宅區(qū)與低級住宅區(qū)的差別(學生答)(教師總結)(教師講解)另外還有行政區(qū)、文化區(qū)等。而在中小城市,這些部門占地面積很小,或者布局分散,形成不了相應的功能 區(qū)。(教師提問)我們把城市功能區(qū)分了好幾種,比如說住宅區(qū),是不是土地都是被居住地占據(jù)呢?是不是就沒有其他的功能了呢?(學生回答)不是(教師總結)不是的。我們說的住宅區(qū)只是在占地面積上,它是占絕大多數(shù),但還是有土地是被其它功能占據(jù)的,比如說住宅區(qū)里的商店、綠化等也要占據(jù)一定的土地, 只是占的比例比較小而已。下面請看書上的活動題。

  • 人教版新課標高中地理必修2第五章第二節(jié)交通運輸布局及其影響教案

    人教版新課標高中地理必修2第五章第二節(jié)交通運輸布局及其影響教案

    (分析:北京的商業(yè)中心分布和變化大致分三個階段:鐘鼓樓市場、三足鼎立格局形成、環(huán)路沿線商業(yè)中心出現(xiàn)。相對應的交通變化,鐘鼓樓市場衰退與大運河運輸?shù)匚凰ヂ洹⑦\輸方式的變化密切相關,后兩個階段與城市交通干線形態(tài)變化緊密聯(lián)系)?!渤修D〕商業(yè)中心的發(fā)展是隨著交通的發(fā)展而變化的,集鎮(zhèn)也是在交通要道上發(fā)展起來 的。(3)對集鎮(zhèn)發(fā)展的影響〔舉例說明〕陜西省勉縣的長林鎮(zhèn),過去地處漢中經褒河去甘肅、四川的必經之路,來往客商眾多,商業(yè)十分繁榮。后來由于改線,集鎮(zhèn)逐漸衰落,至今連定期的集市貿易都沒有了,完全退化為單純的居民點。以及運河沿線城鎮(zhèn)如山東等的興衰,亦可說明交通線的改變對聚落的影響。〔總結〕交通線路的改變常會引起集鎮(zhèn)的繁榮或衰落。

  • 人教版新課標高中地理必修2第五章第一節(jié)交通運輸方式和布局教案

    人教版新課標高中地理必修2第五章第一節(jié)交通運輸方式和布局教案

    (2)修建通向西藏的鐵路,要克服哪些自然障礙?①凍土的季節(jié)凍融作用使路基不穩(wěn)固,也使修路技術難度大,成本高②生態(tài)脆弱,植被破壞后難以修復③高原缺氧,使施工困難④廣布的荒漠,多山的地形都使建設難度加大(3)結合初中所學知識分析,未來穿行于青藏高原鐵路運輸線上的貨車中主要運輸?shù)呢浳镉心男恳喳}湖中礦物為原料的化工產品,有色金屬及其加工產品,畜產品及外省運入的各種工業(yè)品等。【總結新課】交通運輸網的基本要素包括:交通線(鐵路、公路、航道、管道)和交通點(港口、車站、航空港);運輸網有單一和綜合運輸網二種形式。分國家級、省級和大區(qū)級三個層次。交通運輸網的點線布局受經濟、社會、技術和自然等因素的影響。【課后作業(yè)】:完成高一地理第二冊填圖冊 第五章第一節(jié)

  • 人教版高中政治必修4真正的哲學都是自己時代精神上的精華精品教案

    人教版高中政治必修4真正的哲學都是自己時代精神上的精華精品教案

    一、教材分析 《真正的哲學都是自己時代精神上的精華》是人教版高中政治必修四第3章第1框的教學內容,主要學習哲學與時代的關系。二、教學目標1.知識目標:識記哲學是時代的精神上的精華;理解哲學與時代的關系。2.能力目標:培養(yǎng)學生運用哲學理論觀察、分析、處理社會問題的能力,增強學生的時代感。3.情感、態(tài)度和價值觀目標:培養(yǎng)學生與時俱進的思想品質,讓學生關注時代、關注現(xiàn)實、關注生活,逐步樹立科學的世界觀、人生觀、價值觀 。三、教學重點難點哲學與時代的關系。四、學情分析本框題的內容比較抽象,不易理解,所以講解時需要詳細。教師指導學生借助歷史知識進行理解。五、教學方法1.教師啟發(fā)、引導,學生自主閱讀、思考,討論、交流學習成果。2.學案導學:見后面的學案。3.新授課教學基本環(huán)節(jié):預習檢查、總結疑惑→情境導入、展示目標→合作探究、精講點撥→反思總結、當堂檢測→發(fā)導學案、布置預習

  • 人教A版高中數(shù)學必修一函數(shù)的零點與方程的解教學設計(1)

    人教A版高中數(shù)學必修一函數(shù)的零點與方程的解教學設計(1)

    本節(jié)課是新版教材人教A版普通高中課程標準實驗教科書數(shù)學必修1第四章第4.5.1節(jié)《函數(shù)零點與方程的解》,由于學生已經學過一元二次方程與二次函數(shù)的關系,本節(jié)課的內容就是在此基礎上的推廣。從而建立一般的函數(shù)的零點概念,進一步理解零點判定定理及其應用。培養(yǎng)和發(fā)展學生數(shù)學直觀、數(shù)學抽象、邏輯推理和數(shù)學建模的核心素養(yǎng)。1、了解函數(shù)(結合二次函數(shù))零點的概念;2、理 解函數(shù)零點與方程的根以及函數(shù)圖象與x軸交點的關系,掌握零點存在性定理的運用;3、在認識函數(shù)零點的過程中,使學生學會認識事物的特殊性與一般性之間的關系,培養(yǎng)數(shù)學數(shù)形結合及函數(shù)思想; a.數(shù)學抽象:函數(shù)零點的概念;b.邏輯推理:零點判定定理;c.數(shù)學運算:運用零點判定定理確定零點范圍;d.直觀想象:運用圖形判定零點;e.數(shù)學建模:運用函數(shù)的觀點方程的根;

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    古詩詞誦讀《虞美人(春花秋月何時了)》說課稿 2021-2022學年統(tǒng)編版高中語文必修上冊

    (一)說教材 《虞美人》選自高中語文統(tǒng)編版必修上冊·古詩詞誦讀?!队菝廊恕肥窃~中的代表作品,是李煜生命中最為重要的一首詞作,極具藝術魅力,對于陶冶學生的情操,豐富和積淀學生的人文素養(yǎng)意義非凡。(二)說學情總體來說,所教班級的學生基礎不強,學習意識略有偏差,在學習過程中需要教師深入淺出,不斷創(chuàng)造動口、動手、動腦的機會,他們才能更好地達成教學目標。(三)說教學目標根據(jù)教學內容和學情分析,確定如下教學目標(1)探究這首詞的內涵,了解李煜及其創(chuàng)作風格。(2)通過對本詞的品析,提高詞的鑒賞能力。(3)通過對比閱讀,體會李煜詞 “赤子之心” 、“以血書者”的特色,體味其深沉的亡國之恨和故國之思。

  • 拋物線的簡單幾何性質(1)教學設計人教A版高中數(shù)學選擇性必修第一冊

    拋物線的簡單幾何性質(1)教學設計人教A版高中數(shù)學選擇性必修第一冊

    問題導學類比用方程研究橢圓雙曲線幾何性質的過程與方法,y2 = 2px (p>0)你認為應研究拋物線的哪些幾何性質,如何研究這些性質?1. 范圍拋物線 y2 = 2px (p>0) 在 y 軸的右側,開口向右,這條拋物線上的任意一點M 的坐標 (x, y) 的橫坐標滿足不等式 x ≥ 0;當x 的值增大時,|y| 也增大,這說明拋物線向右上方和右下方無限延伸.拋物線是無界曲線.2. 對稱性觀察圖象,不難發(fā)現(xiàn),拋物線 y2 = 2px (p>0)關于 x 軸對稱,我們把拋物線的對稱軸叫做拋物線的軸.拋物線只有一條對稱軸. 3. 頂點拋物線和它軸的交點叫做拋物線的頂點.拋物線的頂點坐標是坐標原點 (0, 0) .4. 離心率拋物線上的點M 到焦點的距離和它到準線的距離的比,叫做拋物線的離心率. 用 e 表示,e = 1.探究如果拋物線的標準方程是〖 y〗^2=-2px(p>0), ②〖 x〗^2=2py(p>0), ③〖 x〗^2=-2py(p>0), ④

  • 雙曲線的簡單幾何性質(2)教學設計人教A版高中數(shù)學選擇性必修第一冊

    雙曲線的簡單幾何性質(2)教學設計人教A版高中數(shù)學選擇性必修第一冊

    二、典例解析例4.如圖,雙曲線型冷卻塔的外形,是雙曲線的一部分,已知塔的總高度為137.5m,塔頂直徑為90m,塔的最小直徑(喉部直徑)為60m,喉部標高112.5m,試建立適當?shù)淖鴺讼担蟪龃穗p曲線的標準方程(精確到1m)解:設雙曲線的標準方程為 ,如圖所示:為喉部直徑,故 ,故雙曲線方程為 .而 的橫坐標為塔頂直徑的一半即 ,其縱坐標為塔的總高度與喉部標高的差即 ,故 ,故 ,所以 ,故雙曲線方程為 .例5.已知點 到定點 的距離和它到定直線l: 的距離的比是 ,則點 的軌跡方程為?解:設點 ,由題知, ,即 .整理得: .請你將例5與橢圓一節(jié)中的例6比較,你有什么發(fā)現(xiàn)?例6、 過雙曲線 的右焦點F2,傾斜角為30度的直線交雙曲線于A,B兩點,求|AB|.分析:求弦長問題有兩種方法:法一:如果交點坐標易求,可直接用兩點間距離公式代入求弦長;法二:但有時為了簡化計算,常設而不求,運用韋達定理來處理.解:由雙曲線的方程得,兩焦點分別為F1(-3,0),F2(3,0).因為直線AB的傾斜角是30°,且直線經過右焦點F2,所以,直線AB的方程為

  • 橢圓的簡單幾何性質(2)教學設計人教A版高中數(shù)學選擇性必修第一冊

    橢圓的簡單幾何性質(2)教學設計人教A版高中數(shù)學選擇性必修第一冊

    二、典例解析例5. 如圖,一種電影放映燈的反射鏡面是旋轉橢圓面(橢圓繞其對稱軸旋轉一周形成的曲面)的一部分。過對稱軸的截口 ABC是橢圓的一部分,燈絲位于橢圓的一個焦點F_1上,片門位另一個焦點F_2上,由橢圓一個焦點F_1 發(fā)出的光線,經過旋轉橢圓面反射后集中到另一個橢圓焦點F_2,已知 〖BC⊥F_1 F〗_2,|F_1 B|=2.8cm, |F_1 F_2 |=4.5cm,試建立適當?shù)钠矫嬷苯亲鴺讼?,求截口ABC所在的橢圓方程(精確到0.1cm)典例解析解:建立如圖所示的平面直角坐標系,設所求橢圓方程為x^2/a^2 +y^2/b^2 =1 (a>b>0) 在Rt ΔBF_1 F_2中,|F_2 B|= √(|F_1 B|^2+|F_1 F_2 |^2 )=√(〖2.8〗^2 〖+4.5〗^2 ) 有橢圓的性質 , |F_1 B|+|F_2 B|=2 a, 所以a=1/2(|F_1 B|+|F_2 B|)=1/2(2.8+√(〖2.8〗^2 〖+4.5〗^2 )) ≈4.1b= √(a^2 〖-c〗^2 ) ≈3.4所以所求橢圓方程為x^2/〖4.1〗^2 +y^2/〖3.4〗^2 =1 利用橢圓的幾何性質求標準方程的思路1.利用橢圓的幾何性質求橢圓的標準方程時,通常采用待定系數(shù)法,其步驟是:(1)確定焦點位置;(2)設出相應橢圓的標準方程(對于焦點位置不確定的橢圓可能有兩種標準方程);(3)根據(jù)已知條件構造關于參數(shù)的關系式,利用方程(組)求參數(shù),列方程(組)時常用的關系式有b2=a2-c2等.

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