
一、教學(xué)重難點(diǎn)有效引導(dǎo)學(xué)生反思本人和父母的情感,回想父母對(duì)本人的付出,表達(dá)對(duì)父母的愛,養(yǎng)成感恩父母、好好學(xué)習(xí)的氛圍。二、教學(xué)流程?。?)導(dǎo)入:1.黑板板書:父母愛 愛父母2.導(dǎo)語(yǔ):同學(xué)們,今天是新學(xué)期開學(xué)的第一天。在父母的關(guān)心下,我們一天天地茁壯生長(zhǎng),今天終于成長(zhǎng)為一名四年級(jí)小學(xué)生了。今天的課,就以“父母愛愛父母”為主題,開展我們的課堂。

佛山石灣陶瓷發(fā)展歷史悠久,為了讓幼兒感受這張靚麗的歷史“名片”的魅力,了解石灣陶瓷栩栩如生的形象和一道道制作工序,在幼兒自己動(dòng)手制作的過(guò)程中掌握簡(jiǎn)單的制作方法,體驗(yàn)成功感并領(lǐng)略石灣陶瓷的藝術(shù)美。

三、科學(xué)育人抓質(zhì)量不是只抓課本知識(shí),而是要從抓習(xí)慣、抓細(xì)節(jié)、抓學(xué)困生、抓讀書等方面入手。抓質(zhì)量要從培養(yǎng)學(xué)生良好的學(xué)習(xí)習(xí)慣入手,良好習(xí)慣的培養(yǎng),只靠班主任一人是心有余而力不足的,需要每一位教師齊心協(xié)力,齊抓共管。抓質(zhì)量要注重細(xì)節(jié),如語(yǔ)文要從生字、背誦開始夯實(shí)基礎(chǔ),數(shù)學(xué)要從基本計(jì)算、每一個(gè)小知識(shí)點(diǎn)、讀題審題點(diǎn)滴落實(shí)。抓好每個(gè)細(xì)節(jié),進(jìn)而形成習(xí)慣,學(xué)生的成績(jī)自然就會(huì)提高。抓質(zhì)量要把目光投向?qū)W困生,如課堂上設(shè)計(jì)一些學(xué)困生能夠回答上來(lái)的問(wèn)題并及時(shí)表?yè)P(yáng)他們,不斷增強(qiáng)自信,課后適當(dāng)開“小灶”,加強(qiáng)指導(dǎo),還要跟蹤輔導(dǎo),持續(xù)關(guān)注,增強(qiáng)他們的學(xué)習(xí)主動(dòng)性和積極性,成績(jī)也會(huì)有提高。抓質(zhì)量還要抓讀書,要培養(yǎng)學(xué)生的讀書興趣,讓讀書成為學(xué)生的生活方式,不僅課上讀,還要在課外讀,不僅讓學(xué)生讀,教師自己更要讀。

1. Ss look at the picture and scan the passage to understand the main idea while teacher is giving the following questions to inspire Ss to think.*Where are those people?*What are they doing?*Why are they so excited?2. Ss complete the passage with the appropriate -ing form. Then discuss and check the answers with class.Answers: boring, interesting, taking, exciting, amazing3. The teacher raises questions for the students to discuss and encourages them to express their opinions.*Do you like La Tomatina? Why or why not?4. Each group representative reports the discussion result, the teacher gives feedback and the evaluation.Step 6 PracticeActivity 41. Ss complete the Ex 2 in Using structures.2. Check the answers after finishing the exercises.①The dragon boat races are the most exciting part of the Dragon Boat Festival.② The children were excited to go Easter egg hunting.③What an amazing performance! This is the best music festival I have ever been to.④We were amazed by her funny-looking hat.⑤His inspiring speech at the conference won the admiration/ favour of the audience.⑥This is a challenging game to test your memory and observation capabilities. 3. T asks Ss to finish Ex 3 and 4 in Using structures by themselves, then check the answers with class.Step 6 Homework1. Understand and master the functions and usage of the -ing form;2. Finish the other exercises in Using structures.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握動(dòng)詞-ing形式作定語(yǔ)和表語(yǔ)的功能和意義;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否在理解文段內(nèi)容的基礎(chǔ)上,根據(jù)上下文語(yǔ)境和表達(dá)邏輯,能正確運(yùn)用動(dòng)詞-ing形式描述節(jié)日慶典。3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否歸納和積累用于表達(dá)情緒的相關(guān)詞匯。

本板塊的活動(dòng)主題是“談?wù)摴?jié)日活動(dòng)”(Talk about festival activities),主要是從貼近學(xué)生日常生活的角度來(lái)切入“節(jié)日”主題。學(xué)生會(huì)聽到發(fā)生在三個(gè)國(guó)家不同節(jié)日?qǐng)鼍跋碌暮?jiǎn)短對(duì)話,對(duì)話中的人們正在參與或?qū)⒁H歷不同的慶祝活動(dòng)。隨著全球化的進(jìn)程加速,國(guó)際交流日益頻繁,無(wú)論是國(guó)人走出國(guó)門還是外國(guó)友人訪問(wèn)中國(guó),都已成為司空見慣的事情。因此,該板塊所選取的三個(gè)典型節(jié)日?qǐng)鼍岸际菍儆诳缥幕浑H語(yǔ)境,不僅每組對(duì)話中的人物來(lái)自不同的文化背景,對(duì)話者的身份和關(guān)系也不盡相同。1. Master the new words related to holiday: the lantern, Carnival, costume, dress(sb)up, march, congratulation, congratulate, riddle, ceremony, samba, make - up, after all. 2. To understand the origin of major world festivals and the activities held to celebrate them and the significance of these activities;3. Improve listening comprehension and oral expression of the topic by listening and talking about traditional festivals around the world;4. Improve my understanding of the topic by watching pictures and videos about different traditional festivals around the world;5. Review the common assimilation phenomenon in English phonetics, can distinguish the assimilated phonemes in the natural language flow, and consciously use the assimilation skill in oral expression. Importance:1. Guide students to pay attention to the attitude of the speaker in the process of listening, and identify the relationship between the characters;2. Inspire students to use topic words to describe the festival activities based on their background knowledge. Difficulties:In the process of listening to the correct understanding of the speaker's attitude, accurately identify the relationship between the characters.

Activity 41. Students complete the task of activity 4, then teachers and students check the answers. 2. The teacher organized the students to work together and asked them to use the tables and mind maps sorted out before to retold the important choices in Lin Qiaozhi's life and their resultsStep 5 Language points1. The teacher asks the students to read the text carefully, find out the core words and long and difficult sentences in the text and draw lines, understand the use of vocabulary, and analyze the structure of long and difficult sentences. 2. The teacher explains and summarizes the usage of core vocabulary and asks the students to take notes. 3. The teacher analyzes and explains the long and difficult sentences that the students don't understand, so that the students can understand them better. Step 6 Homework1. Read the text again, in-depth understanding of the text; 2. Master the use of core vocabulary and understand the long and difficult sentences. 3. Complete relevant exercises in the guide plan. 1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握閱讀文本中的新詞匯的意義與用法;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否結(jié)合文本特點(diǎn)總結(jié)林巧稚的人生原則和人格品質(zhì)特征;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否針對(duì)人生抉擇發(fā)表自己的看法;能否全面地、客觀地、理性地看待問(wèn)題,進(jìn)而對(duì)道德和人性有更加深入的思考和理解。

*wide range of origins(= a great number of different origins, many kinds of origins)*It featured a parade and a great feast with music, dancing, and sports. (=A parade and a great feast with music, dancing, and sports were included as important parts of the Egyptian harvest festival.)*.. some traditions may fade away and others may be established.(= Some traditions may disappear gradually, while other new traditions may come into being.)Step 6 Practice(1) Listen and follow the tape.The teacher may remind the students to pay attention to the meaning and usage of the black words in the context, so as to prepare for the completion of the blanks in activity 5 and vocabulary exercises in the exercise book.(2) Students complete the text of activity 5 by themselves.The teacher needs to remind the students to fill in the blanks with the correct form of the vocabulary they have learned in the text.Students exchange their answers with their partners, and then teachers and students check their answers.(3)Finish the Ex in Activity 5 of students’ book.Step 7 Homework1. Read the text again, in-depth understanding of the text;2. Discuss the origin of festivals, the historical changes of related customs, the influence of commercial society on festivals and the connotation and essential meaning of festivals.3. Complete relevant exercises in the guide plan.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握閱讀文本中的新詞匯的意義與用法;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否結(jié)合文本特點(diǎn)快速而準(zhǔn)確地找到主題句;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否理清論說(shuō)文的語(yǔ)篇結(jié)構(gòu)和文本邏輯,了解節(jié)日風(fēng)俗發(fā)展與變遷,感悟節(jié)日的內(nèi)涵與意義。

The joke set her crying.這個(gè)玩笑使她哭起來(lái)。Step 5 ReadingActivity 31. Students read the small text in activity 3. The teacher provides several small questions to check whether students understand the content of the text and the ideographic function of the -ing form in the text.*Where are those people?*Why did Dr Bethune come to China?*How did he help the Chinese people during the war?*What did Chairman Mao Zedong say about him?2. Ss try to rewrite some sentences using the -ing form. Then check the answers. When checking the answers, the teacher can ask different students to read the rewritten sentences and give comments.Answers:1. he became very interested in medicine, deciding to become a doctor.2. …after hearing that many people were dying in the war.3. Helping to organise hospitals, he taught doctors and nurses, and showed people how to give first aid./ He helped to organise hospitals, teaching doctors and nurses, and showing people how to give first aid.4. …praising Dr Bethune as a hero to be remembered in China.Step 6 PracticeActivity 4Students complete grammar activities 2 and 3 on page 69 of the workbook.Step 6 Homework1. Understand and master the functions and usage of the -ing form;2. Finish the other exercises in Using structures.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握動(dòng)詞-ing形式作賓語(yǔ)補(bǔ)足語(yǔ)語(yǔ)和狀語(yǔ)語(yǔ)的功能和意義;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否正確使用動(dòng)詞-ing形式描述人物的行為、動(dòng)作及其經(jīng)歷;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否獨(dú)立完成練習(xí)冊(cè)和導(dǎo)學(xué)案中的相關(guān)練習(xí)。

3.Teachers ask different groups to report the answers to the questions and ask them to try different sentence patterns.The teacher added some sentence patterns for students to refer to when writing.Step 4 Writing taskActivity 51.Write the first draft.Students first review the evaluation criteria in activity 5, and then independently complete the draft according to the outline of activity 4, the answers to the questions listed in the group discussion and report, and the reference sentence pattern.2.Change partners.The teacher guides the students to evaluate their partner's composition according to the checklist of activity 5 and proposes Suggestions for modification.3.Finalize the draft.Based on the peer evaluation, students revise their own compositions and determine the final draft.Finally, through group recommendation, the teacher selects excellent compositions for projection display or reading aloud in class, and gives comments and Suggestions.Step 5 Showing writingActivity 5T call some Ss to share their writing.Step 6 Homework1. Read the passage in this section to better understand the passage.2. Carefully understand the hierarchical structure of the article, and deeply understand the plot of the story according to the causes, process and results;3. Independently complete the relevant exercises in the guide plan.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握閱讀文本中的新詞匯的意義與用法;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否通過(guò)人物言行的對(duì)比分析道德故事的深層內(nèi)涵;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否根據(jù)故事的起因、經(jīng)過(guò)和結(jié)果來(lái)深入理解故事的情節(jié),從而了解文章的層次結(jié)構(gòu);4、結(jié)合現(xiàn)實(shí)生活案例發(fā)表自己的見解和看法,寫一篇觀點(diǎn)明確、層次分明的故事評(píng)論。

(2) students are divided into groups according to the requirements of activity 3. Each student shares a story of personal experience or hearing-witnessing kindness, and then selects the most touching story in the group and shares it with the whole class. Before the students share the story, the teacher can instruct them to use the words and sentence patterns in the box to express. For example, the words in the box can be classified:Time order: first of all, then, after that, later, finally logical relationship :so, however, although, butTeachers can also appropriately add some transitional language to enrich students' expression:Afterwards, afterwards, at last, in the end, eventuallySpatial order: next to, far from, on the left, in front ofOtherwise, nevertheless, as a result, therefore, furthermore, in addition, as well asSummary: in a word, in short, on the whole, to sum up, in briefStep 8 Homework1. Understand the definition of "moral dilemma" and establish a correct moral view;2. Accumulate vocabulary about attitudes and emotions in listening texts and use them to express your own views;3. Complete relevant exercises in the guide plan.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否理解理解“道德困境”的定義;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否通過(guò)說(shuō)話人所表達(dá)的內(nèi)容、說(shuō)話的語(yǔ)氣、語(yǔ)調(diào)等來(lái)判斷其態(tài)度和情緒;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否針對(duì)具體的道德困境發(fā)表自己的看法和見解,能否掌握聽力理訓(xùn)練中的聽力策略。

The price is the same as(the price was)before the war.價(jià)格與戰(zhàn)前相同。(4)定語(yǔ)從句中的“關(guān)系代詞+助動(dòng)詞be”可以省略。The ticket(that/which was)booked by his sister has been sent to him.他妹妹訂的那張票已送到了他那里。Step 5 PracticeActivity 3(1) Guide students to complete the four activities in the Using Structures part of exercise book, in which activities 1 and 2 focus on ellipsis in dialogue answers, activity 3 focus on signs and headlines, two typical situations where ellipsis is used, and activity 4 focus on ellipsis in diary, an informal style.(2) Combine the examples in the above activities, ask students to summarize the omitted situations in groups, and make their own summary into a poster, and post it on the class wall after class to share with the class.(This step should give full play to the subjectivity of students, and teachers should encourage students to conclude different ellipsis phenomena according to their own understanding, they can conclude according to the different parts omitted in the sentence.)Step 6 Homework1. Understand and master the usages of ellipsis;2. Finish the other exercises in Using structures of Workbook.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握省略的用法;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否根據(jù)上下文語(yǔ)境或情景恢復(fù)句子中省略的成分,體會(huì)使用省略的效果;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否獨(dú)立完成練習(xí)冊(cè)和導(dǎo)學(xué)案中的相關(guān)練習(xí)。

(2)Consolidate key vocabulary.Ask the students to complete the exercises of activity 6 by themselves. Then ask them to check the answers with their partners.(The first language:Damage of the 1906 San Francisco earthquake and fire.A second language: Yunnan - one of the most diverse provinces in China).Step 5 Language points1. The teacher asks the students to read the text carefully, find out the more words and long and difficult sentences in the text and draw lines, understand the use of vocabulary, and analyze the structure of long and difficult sentences.2. The teacher explains and summarizes the usage of core vocabulary and asks the students to take notes.3. The teacher analyzes and explains the long and difficult sentences that the students don't understand, so that the students can understand them better.Step 6 Homework1. Read the text again, in-depth understanding of the text;2. Master the use of core vocabulary and understand the long and difficult sentences.3. Complete relevant exercises in the guide plan.1、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生是否理解和掌握閱讀文本中的新詞匯的意義與用法;2、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否結(jié)合文本特點(diǎn)了解文章的結(jié)構(gòu)和作者的寫作邏輯;3、通過(guò)本節(jié)內(nèi)容學(xué)習(xí),學(xué)生能否了解舊金山的城市風(fēng)貌、文化特色,以及加利福尼亞州的歷史,體會(huì)多元文化對(duì)美國(guó)的影響。

該板塊的活動(dòng)主題是“介紹一個(gè)有顯著文化特征的地方”( Describe a place with distinctive cultural identity)。該板塊通過(guò)介紹中國(guó)城繼續(xù)聚焦中國(guó)文化。本單元主題圖呈現(xiàn)的是舊金山中國(guó)城的典型景象, Reading and Thinking部分也提到中國(guó)城,為該板塊作鋪墊。介紹中國(guó)城的目的主要是體現(xiàn)中國(guó)文化與美國(guó)多元文化的關(guān)系,它是美國(guó)多元文化的重要組成部分。中國(guó)城也是海外華人的精神家園和傳播中國(guó)文化的重要窗口,外國(guó)人在中國(guó)城能近距離體驗(yàn)中國(guó)文化。1. Read the text to understand the cultural characteristics of Chinatown in San Francisco and the relationship between Chinese culture and American multiculturalism;2. Through reading, learn to comb the main information of the article, understand the author's writing purpose and writing characteristics;3. Learn to give a comprehensive, accurate, and organized description of the city or town you live in;Learn to revise and evaluate your writing.Importance:1. Guide the students to read the introduction of Chinatown in San Francisco and grasp its writing characteristics;2. Guide students to introduce their city or town in a comprehensive, accurate and organized way;3. Learn to comb the main information of the article, understand the author's writing purpose, and master the core vocabulary.

Activity 81.Grasp the main idea of the listening.Listen to the tape and answer the following questions:Who are the two speakers in the listening? What is their relationship?What is the main idea of the first part of the listening? How about the second part?2.Complete the passage.Ask the students to quickly review the summaries of the two listening materials in activity 2. Then play the recording for the second time.Ask them to complete the passage and fill in the blanks.3.Play the recording again and ask the students to use the structure diagram to comb the information structure in the listening.(While listening, take notes. Capture key information quickly and accurately.)Step 8 Talking Activity 91.Focus on the listening text.Listen to the students and listen to the tape. Let them understand the attitudes of Wu Yue and Justin in the conversation.How does Wu Yue feel about Chinese minority cultures?What does Justin think of the Miao and Dong cultures?How do you know that?2.learn functional items that express concerns.Ask students to focus on the expressions listed in activity. 3.And try to analyze the meaning they convey, including praise (Super!).Agree (Exactly!)"(You're kidding.!)Tell me more about it. Tell me more about it.For example, "Yeah Sure." "Definitely!" "Certainly!" "No kidding!" "No wonder!" and so on.4.Ask the students to have conversations in small groups, acting as Jsim and his friends.Justin shares his travels in Guizhou with friends and his thoughts;Justin's friends should give appropriate feedback, express their interest in relevant information, and ask for information when necessary.In order to enrich the dialogue, teachers can expand and supplement the introduction of Miao, dong, Lusheng and Dong Dage.After the group practice, the teacher can choose several groups of students to show, and let the rest of the students listen carefully, after listening to the best performance of the group, and give at least two reasons.

4.已知△ABC三個(gè)頂點(diǎn)坐標(biāo)A(-1,3),B(-3,0),C(1,2),求△ABC的面積S.【解析】由直線方程的兩點(diǎn)式得直線BC的方程為 = ,即x-2y+3=0,由兩點(diǎn)間距離公式得|BC|= ,點(diǎn)A到BC的距離為d,即為BC邊上的高,d= ,所以S= |BC|·d= ×2 × =4,即△ABC的面積為4.5.已知直線l經(jīng)過(guò)點(diǎn)P(0,2),且A(1,1),B(-3,1)兩點(diǎn)到直線l的距離相等,求直線l的方程.解:(方法一)∵點(diǎn)A(1,1)與B(-3,1)到y(tǒng)軸的距離不相等,∴直線l的斜率存在,設(shè)為k.又直線l在y軸上的截距為2,則直線l的方程為y=kx+2,即kx-y+2=0.由點(diǎn)A(1,1)與B(-3,1)到直線l的距離相等,∴直線l的方程是y=2或x-y+2=0.得("|" k"-" 1+2"|" )/√(k^2+1)=("|-" 3k"-" 1+2"|" )/√(k^2+1),解得k=0或k=1.(方法二)當(dāng)直線l過(guò)線段AB的中點(diǎn)時(shí),A,B兩點(diǎn)到直線l的距離相等.∵AB的中點(diǎn)是(-1,1),又直線l過(guò)點(diǎn)P(0,2),∴直線l的方程是x-y+2=0.當(dāng)直線l∥AB時(shí),A,B兩點(diǎn)到直線l的距離相等.∵直線AB的斜率為0,∴直線l的斜率為0,∴直線l的方程為y=2.綜上所述,滿足條件的直線l的方程是x-y+2=0或y=2.

(2)l的傾斜角為90°,即l平行于y軸,所以m+1=2m,得m=1.延伸探究1 本例條件不變,試求直線l的傾斜角為銳角時(shí)實(shí)數(shù)m的取值范圍.解:由題意知(m"-" 1"-" 1)/(m+1"-" 2m)>0,解得1<m<2.延伸探究2 若將本例中的“N(2m,1)”改為“N(3m,2m)”,其他條件不變,結(jié)果如何?解:(1)由題意知(m"-" 1"-" 2m)/(m+1"-" 3m)=1,解得m=2.(2)由題意知m+1=3m,解得m=1/2.直線斜率的計(jì)算方法(1)判斷兩點(diǎn)的橫坐標(biāo)是否相等,若相等,則直線的斜率不存在.(2)若兩點(diǎn)的橫坐標(biāo)不相等,則可以用斜率公式k=(y_2 "-" y_1)/(x_2 "-" x_1 )(其中x1≠x2)進(jìn)行計(jì)算.金題典例 光線從點(diǎn)A(2,1)射到y(tǒng)軸上的點(diǎn)Q,經(jīng)y軸反射后過(guò)點(diǎn)B(4,3),試求點(diǎn)Q的坐標(biāo)及入射光線的斜率.解:(方法1)設(shè)Q(0,y),則由題意得kQA=-kQB.∵kQA=(1"-" y)/2,kQB=(3"-" y)/4,∴(1"-" y)/2=-(3"-" y)/4.解得y=5/3,即點(diǎn)Q的坐標(biāo)為 0,5/3 ,∴k入=kQA=(1"-" y)/2=-1/3.(方法2)設(shè)Q(0,y),如圖,點(diǎn)B(4,3)關(guān)于y軸的對(duì)稱點(diǎn)為B'(-4,3), kAB'=(1"-" 3)/(2+4)=-1/3,由題意得,A、Q、B'三點(diǎn)共線.從而入射光線的斜率為kAQ=kAB'=-1/3.所以,有(1"-" y)/2=(1"-" 3)/(2+4),解得y=5/3,點(diǎn)Q的坐標(biāo)為(0,5/3).

一、情境導(dǎo)學(xué)前面我們已經(jīng)得到了兩點(diǎn)間的距離公式,點(diǎn)到直線的距離公式,關(guān)于平面上的距離問(wèn)題,兩條直線間的距離也是值得研究的。思考1:立定跳遠(yuǎn)測(cè)量的什么距離?A.兩平行線的距離 B.點(diǎn)到直線的距離 C. 點(diǎn)到點(diǎn)的距離二、探究新知思考2:已知兩條平行直線l_1,l_2的方程,如何求l_1 〖與l〗_2間的距離?根據(jù)兩條平行直線間距離的含義,在直線l_1上取任一點(diǎn)P(x_0,y_0 ),,點(diǎn)P(x_0,y_0 )到直線l_2的距離就是直線l_1與直線l_2間的距離,這樣求兩條平行線間的距離就轉(zhuǎn)化為求點(diǎn)到直線的距離。兩條平行直線間的距離1. 定義:夾在兩平行線間的__________的長(zhǎng).公垂線段2. 圖示: 3. 求法:轉(zhuǎn)化為點(diǎn)到直線的距離.1.原點(diǎn)到直線x+2y-5=0的距離是( )A.2 B.3 C.2 D.5D [d=|-5|12+22=5.選D.]

1.直線2x+y+8=0和直線x+y-1=0的交點(diǎn)坐標(biāo)是( )A.(-9,-10) B.(-9,10) C.(9,10) D.(9,-10)解析:解方程組{■(2x+y+8=0"," @x+y"-" 1=0"," )┤得{■(x="-" 9"," @y=10"," )┤即交點(diǎn)坐標(biāo)是(-9,10).答案:B 2.直線2x+3y-k=0和直線x-ky+12=0的交點(diǎn)在x軸上,則k的值為( )A.-24 B.24 C.6 D.± 6解析:∵直線2x+3y-k=0和直線x-ky+12=0的交點(diǎn)在x軸上,可設(shè)交點(diǎn)坐標(biāo)為(a,0),∴{■(2a"-" k=0"," @a+12=0"," )┤解得{■(a="-" 12"," @k="-" 24"," )┤故選A.答案:A 3.已知直線l1:ax+y-6=0與l2:x+(a-2)y+a-1=0相交于點(diǎn)P,若l1⊥l2,則點(diǎn)P的坐標(biāo)為 . 解析:∵直線l1:ax+y-6=0與l2:x+(a-2)y+a-1=0相交于點(diǎn)P,且l1⊥l2,∴a×1+1×(a-2)=0,解得a=1,聯(lián)立方程{■(x+y"-" 6=0"," @x"-" y=0"," )┤易得x=3,y=3,∴點(diǎn)P的坐標(biāo)為(3,3).答案:(3,3) 4.求證:不論m為何值,直線(m-1)x+(2m-1)y=m-5都通過(guò)一定點(diǎn). 證明:將原方程按m的降冪排列,整理得(x+2y-1)m-(x+y-5)=0,此式對(duì)于m的任意實(shí)數(shù)值都成立,根據(jù)恒等式的要求,m的一次項(xiàng)系數(shù)與常數(shù)項(xiàng)均等于零,故有{■(x+2y"-" 1=0"," @x+y"-" 5=0"," )┤解得{■(x=9"," @y="-" 4"." )┤

新知探究我們知道,等差數(shù)列的特征是“從第2項(xiàng)起,每一項(xiàng)與它的前一項(xiàng)的差都等于同一個(gè)常數(shù)” 。類比等差數(shù)列的研究思路和方法,從運(yùn)算的角度出發(fā),你覺得還有怎樣的數(shù)列是值得研究的?1.兩河流域發(fā)掘的古巴比倫時(shí)期的泥版上記錄了下面的數(shù)列:9,9^2,9^3,…,9^10; ①100,100^2,100^3,…,100^10; ②5,5^2,5^3,…,5^10. ③2.《莊子·天下》中提到:“一尺之錘,日取其半,萬(wàn)世不竭.”如果把“一尺之錘”的長(zhǎng)度看成單位“1”,那么從第1天開始,每天得到的“錘”的長(zhǎng)度依次是1/2,1/4,1/8,1/16,1/32,… ④3.在營(yíng)養(yǎng)和生存空間沒(méi)有限制的情況下,某種細(xì)菌每20 min 就通過(guò)分裂繁殖一代,那么一個(gè)這種細(xì)菌從第1次分裂開始,各次分裂產(chǎn)生的后代個(gè)數(shù)依次是2,4,8,16,32,64,… ⑤4.某人存入銀行a元,存期為5年,年利率為 r ,那么按照復(fù)利,他5年內(nèi)每年末得到的本利和分別是a(1+r),a〖(1+r)〗^2,a〖(1+r)〗^3,a〖(1+r)〗^4,a〖(1+r)〗^5 ⑥

高斯(Gauss,1777-1855),德國(guó)數(shù)學(xué)家,近代數(shù)學(xué)的奠基者之一. 他在天文學(xué)、大地測(cè)量學(xué)、磁學(xué)、光學(xué)等領(lǐng)域都做出過(guò)杰出貢獻(xiàn). 問(wèn)題1:為什么1+100=2+99=…=50+51呢?這是巧合嗎?試從數(shù)列角度給出解釋.高斯的算法:(1+100)+(2+99)+…+(50+51)= 101×50=5050高斯的算法實(shí)際上解決了求等差數(shù)列:1,2,3,…,n,"… " 前100項(xiàng)的和問(wèn)題.等差數(shù)列中,下標(biāo)和相等的兩項(xiàng)和相等.設(shè) an=n,則 a1=1,a2=2,a3=3,…如果數(shù)列{an} 是等差數(shù)列,p,q,s,t∈N*,且 p+q=s+t,則 ap+aq=as+at 可得:a_1+a_100=a_2+a_99=?=a_50+a_51問(wèn)題2: 你能用上述方法計(jì)算1+2+3+… +101嗎?問(wèn)題3: 你能計(jì)算1+2+3+… +n嗎?需要對(duì)項(xiàng)數(shù)的奇偶進(jìn)行分類討論.當(dāng)n為偶數(shù)時(shí), S_n=(1+n)+[(2+(n-1)]+?+[(n/2+(n/2-1)]=(1+n)+(1+n)…+(1+n)=n/2 (1+n) =(n(1+n))/2當(dāng)n為奇數(shù)數(shù)時(shí), n-1為偶數(shù)
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