八年级下册学海风暴
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学海风暴八年级下册英语听写本早读本答案1、Jim is a(n) _______. He is very careful and likes to work with numbers. [单选题] *A. secretaryB. tour guideC. accountant(正确答案)D. English teacher2、It’s usually windy in spring, ______ you can see lots of people flying kites.()[单选题] *A. so(正确答案)B. orC. butD. for3、In 2019 we moved to Boston,()my grandparents are living. [单选题] *A. whoB. whenC. where(正确答案)D. for which4、Grandpa pointed to the hospital and said, “That’s _______ I was born?”[单选题] *A. whenB. howC. whyD. where(正确答案)5、I do not have my own room,_____. [单选题] *A. neither does Tom(正确答案)B. neither has TomC. so does TomD. so has Tom6、_____ yuan a month _____ not enough for a family of three to live on today. [单选题] *A. Five hundred; is(正确答案)B. Five hundreds; areC. Five hundred; areD.Five hundreds; is7、_______ your help, I can’t finish my job. [单选题] *A. withB. without(正确答案)C. inD. into8、Three ______ died of water pollution last winter. [单选题] *A. hundreds of villagersB. hundred villagers(正确答案)C. hundreds villagersD. hundred of villagers9、31.That's ______ interesting football game. We are all excited. [单选题] *A.aB.an(正确答案)C.theD./10、87.—Could you? ? ? ? ? ? me the way to the nearest hospital?—Sure. [单选题] * A.askB.tell(正确答案)C.talkD.speak11、It’s raining heavily outside. Don’t leave _______ it stops. [单选题] *A. whileB. sinceC. until(正确答案)D. when12、Jim will _______ New York at 12 o’clock. [单选题] *A. get onB. get outC. get offD. get to(正确答案)13、Ordinary books, _________ correctly, can give you much knowledge. [单选题] *A. used(正确答案)B. to useC. usingD. use14、—Why do you call him Mr. Know?—______ he knows almost everything that we want to know.()[单选题] *A. SoB. OrC. ButD. Because(正确答案)15、He _______ maths. [单选题] *A. does well in(正确答案)B. good atC. is well inD. does well at16、He often comes to work early and he is _______ late for work. [单选题] *A. usuallyB. never(正确答案)C. oftenD. sometimes17、Though my best friend Jack doesn’t get()education, he is knowledgeable. [单选题] *A. ManyB. littleC. fewD. much(正确答案)18、65.There is a big sale on in the shop! Every-thing is ________ price. [单选题] * A.bigB.fullC.zeroD.half(正确答案)19、71.How beautiful the shoes look! Can I________?[单选题] *A.try it onB.try on itC.try them on(正确答案)D.try on them20、The children are playing wildly and making a lot of?_______. [单选题] *A. cryB. voicesC. noises(正确答案)D. music21、Every morning John takes a()to his office. [单选题] *A. 20-minutes' walkB. 20 minute ' walkC. 20-minutes walkD. 20-minute walk(正确答案)22、———Must I return the book you lent me to you now? ——No, you( ). You can keep it for another few days. [单选题] *A.can’tB. shouldn'tC. mustn'tD. don, t have to(正确答案)23、Allen is looking forward to _______ his American partner at the trade fair. [单选题] *A. meetB. meeting(正确答案)C. be meetingD. having meeting24、69.Online shopping is easy, but ________ in the supermarket usually ________ a lot of time. [单选题] *A.shop; takesB.shopping; takeC.shop; takeD.shopping; takes(正确答案)25、—What do you think of Animal World? —______. I watch it every day.()[单选题] *A. I don’t mind it.B. I like it.(正确答案)C. I can’t stand it.D. I don’t like it.26、In winter, animals have a hard time_____anything to eat. [单选题] *A.to findB.finding(正确答案)C.foundD.to finding27、--Jenny, what’s your favorite _______?--I like potatoes best. [单选题] *A. fruitB. vegetable(正确答案)C. drinkD. meat28、My dog is very _______. It is safe to touch it if you want to. [单选题] *A. luckyB. deliciousC. friendly(正确答案)D. helpful29、--Don’t _______ too late, or you will feel tired in class.--I won’t, Mum. [单选题] *A. call upB. wake upC. stay up(正确答案)D. get up30、--Do you have a _______?--Yes, I _______ at a clothes store. [单选题] *A. work; workB. work; jobC. job; jobD. job; work(正确答案)。
听力材料及答案语法专练一,1,staying 2,reading3,making4.Being5.piaying二,1.-5BDBDD三,1.listening to tapes 2,by me 3.by the window 4.by six o’clock 5.Reading more books Section A(1a-2d)课内基础闯关一.Driving 2 to improve 3.to make/made 4.reading 5.learning二,1-5DBBCC三.1.word by word 2Reading aloud 3.learned a lot 4.too ;to 5.The earlier;the more easily课外拓展提高一.1.textbooks 2.aloud 3.pronunciation 4.conversations 5.patient二.1-5AADBC三.1-5CDBBC6-10ACAAB11-15.CDDBDSection A(3a-4c)课内基础闯关一.1,grammar 2repeat 3.expressions 4.improve 5.discovered二.1-5DCCBD三.1.memorize;talking notes 2.so;that 3.anything special 4.beacuse of 5.fell in love with课外拓展提高一.1.ask;for 2.was afraid to 3.look;up 4.take notes 5.Beacuse of二.1-5CBCDB三.1-5.CADDDSection B(1a-1e)课内基础闯关一.1.pronounce 2.writing 3.mistakes 4understood 5.make二.1-5BBDBC三.1.how to answer 2.lots of challenges 3.make mistakes 4.forgets to do 5.to get the pronunciation课外拓展提高一.1.mistakes 2.partner 3.increase 4.spoken 5.pronounce二.1-5.ACBAC三.1.best 2.when 3.in 4.difficult 5.something 6.If 7.say 8.seeing 9.well 10.allSection B(2a-2e)课内基础闯关一.1.wisely 2.reviewing 3.learner 4.interested 5.successful二.1-5DDCCD三.1.depend on 2.pay attention to 3.agree with 4.thinking about 5.successful;succeed课外拓展提高一.1.attention 2.connect 3.overnight 4.create 5increased二.1-5BBDBB三.1-5BDCCASection B(3a-Self Check)课内基础闯关一.1.remember 2.preparing 3.brain 4.matter rmation二.1-5CCCAB三.1.looking for2.at once 3.stressed out 4.remember calling 5.Keep reading课外拓展提高一.1.connect;with 2.pay attention to 3.be afraid to 4.learnt/learned to 5.taking notes 二.1-5CBBAA三.1-5DAEBG中考真题点播1-5ACCBD 6-10ACDBDUnit 2。
八年级下册英语学海风暴RJ人教版答案20221、The soldiers would rather die than give in. [单选题] *A. 呈交B. 放弃C. 泄露D. 投降(正确答案)2、The boy’s mother always _______ him a story before he goes to bed. [单选题] *A. saysB. speaksC. tells(正确答案)D. talks3、21 In a few years' time, there ________ thousands of trees on the hill. [单选题] * A.will haveB.will be(正确答案)C.are haveD.have4、On Easter children _______ eggs around the house. [单选题] *A. hunt for(正确答案)B. send forC. prepare forD. ask for5、Marie is a _______ girl.She always smiles and says hello to others. [单选题] *A. shyB. friendly(正确答案)C. healthyD. crazy6、In order to find the missing child, villagers _______ all they can over the past five hours. [单选题] *A. didB. doC. had doneD. have been doing(正确答案)7、15.The restaurant ________ many complaints because of the terrible service since last month. [单选题] *A.receivesB.is receivingC.has received(正确答案)D.will receive8、Which is _______ city, Shanghai, Beijing or Chengdu? [单选题] *A. largeB. largerC. largestD. the largest(正确答案)9、Mary wanted to travel around the world all by herself, but her parents did not _______ her to do so. [单选题] *A. forbidB. allowC. follow(正确答案)D. ask10、1——May I help you? You seem to be having some problems.——_______ , thanks. Ithink I can manage. [单选题] *A. All rightB. No problemC. It’s all right(正确答案)D. There’s no way11、--It is Sunday tomorrow, I have no idea what to do.--What about _______? [单选题] *A. play computer gamesB. go fishingC. climbing the mountain(正确答案)D. see a film12、The house is well decorated _____ the disarrangement of a few photos. [单选题] *A. exceptB. besidesC. except for(正确答案)D. in addition to13、The hall in our school is _____ to hold 500 people. [单选题] *A. big enough(正确答案)B. enough bigC. very smallD. very big14、Sichuan used to have more people than ______ province in China. [单选题] *A. otherB. any other(正确答案)C. anotherD. any others15、Modern plastics can()very high and very low temperatures. [单选题] *A. stand(正确答案)B. sustainC. carryD. support16、Though my best friend Jack doesn’t get()education, he is knowledgeable. [单选题] *A. ManyB. littleC. fewD. much(正确答案)17、Kids will soon get tired of learning _____ more than they can. [单选题] *A. if they expect to learnB. if they are expected to learn(正确答案)C. if they learn to expectD. if they are learned to expect18、They will hold the party if they _____ the project on time. [单选题] *A. will completeB. complete(正确答案)C.completedD. had completed19、Mary _______ a small gift yesterday, but she didn’t _______ it. [单选题] *A. accepted; receiveB. received; accept(正确答案)C. receives; acceptedD. accepts; received20、You can buy some pieces of bread from "_______". [单选题] *A. Bakery(正确答案)B. Travel AgencyC. LaundryD. Ticket Office21、Tom sits _______ Mary and Jane. [单选题] *A. amongB. between(正确答案)C. onD. next22、( ) The salesgirls in Xiushui Market have set a good example______us in learning English. [单选题] *A. to(正确答案)B. forC. withD. on23、It is important for us _______ English well. [单选题] *A. learnB. learningC. to learn(正确答案)D. learned24、Three ______ died of water pollution last winter. [单选题] *A. hundreds of villagersB. hundred villagers(正确答案)C. hundreds villagersD. hundred of villagers25、He was very excited to read the news _____ Mo Yan had won the Nobel Prize for literature [单选题] *A. whichB. whatC. howD. that(正确答案)26、—Why do you look so ______?—Our team won the basketball match!()[单选题] *A. angryB. excited(正确答案)C. nervousD. unfair27、37.It’s fun _________ a horse with your best friends on the grass. [单选题] *A.to ride (正确答案)B.ridingC.ridesD.ride28、—Mum, could you buy a schoolbag ______ me when you go shopping?—No problem.()[单选题] *A. ofB. toC. inD. for(正确答案)29、31.That's ______ interesting football game. We are all excited. [单选题] *A.aB.an(正确答案)C.theD./30、Many people prefer the bowls made of steel to the _____ made of plastic. [单选题] *A. itB. ones(正确答案)C. oneD. them。
一、选择题1. 下列词语中,字形、字音、词义完全正确的一项是()A. 沧海一粟翠色欲流B. 恣意妄为雅俗共赏C. 纤尘不染震耳欲聋D. 漫不经心美轮美奂2. 下列句子中,没有语病的一项是()A. 通过这次活动,同学们不仅提高了思想觉悟,还增强了实践能力。
B. 他虽然学习很努力,但是成绩却一直不理想。
C. 这本书的内容丰富,语言生动,插图精美,深受同学们的喜爱。
D. 随着科技的发展,我们的生活水平得到了极大的提高,因此我们应该更加珍惜现在的幸福生活。
3. 下列词语中,形近音近但意思不同的一项是()A. 谦逊谦虚B. 恣意纵情C. 雅致雅俗D. 恣肆恣意4. 下列句子中,使用了修辞手法的一项是()A. 夜幕降临,华灯初上,整个城市变得灯火辉煌。
B. 春风拂面,温暖如春。
C. 山清水秀,鸟语花香。
D. 雨过天晴,彩虹挂在天空。
5. 下列词语中,与“日新月异”意思相近的一项是()A. 一日千里B. 沉默寡言C. 风和日丽D. 草长莺飞二、填空题6. 下列名句的空缺处应填入的词语是()(1)______江山,一片神工。
(李白《望庐山瀑布》)(2)______随春草,明年还生。
(白居易《赋得古原草送别》)(3)______江水,海内存知己。
(王勃《滕王阁序》)7. 下列词语中,与下列句子中的词语意义相近的一项是()(1)雄关漫道真如铁,而今迈步从头越。
()(2)会当凌绝顶,一览众山小。
()(3)春眠不觉晓,处处闻啼鸟。
()三、简答题8. 请简述《岳阳楼记》中“先天下之忧而忧,后天下之乐而乐”这句话的内涵。
9. 请简要分析《庐山谣》中“飞流直下三千尺,疑是银河落九天”这句话的意境。
10. 请结合《赋得古原草送别》中的诗句,谈谈你对“离愁”的理解。
四、作文11. 请以“家乡的变化”为题,写一篇不少于500字的作文。
注意:卷面整洁,书写规范,内容充实,条理清晰。
学海风暴八下英语人教版第一单元试卷作文Embarking on the journey of learning a new language is akin to setting sail on the vast ocean of knowledge. The waves of grammar rules and the winds of vocabulary can be challenging, but with determination and practice, one can navigate through to fluency. In the realm of English education, the "People's Education Edition: English for Junior High School (Grade 8, Volume 2)" serves as a compass, guiding learners through the intricacies of the language.The first unit of this educational series is a beacon for beginners, illuminating the path with its comprehensive approach to language learning. It emphasizes the importance of building a strong foundation in the four key skills: listening, speaking, reading, and writing. Each skill is a cardinal point on the compass of language learning, and mastery of these directs students towards effective communication.In the context of writing, the unit encourages students to express their thoughts coherently and creatively. Writing is not merely about stringing words together; it's about weaving a tapestry of ideas that resonate with clarity and purpose. To write effectively, one must understand the structure of the language, the nuances of tone, and the rhythm of sentences.Consider the following narrative, crafted to embody the principles taught in the unit:As the sun dipped below the horizon, casting a golden glow over the city, Emma stood at the edge of the rooftop garden, her eyes reflecting the twilight. She had always found solace in the quiet moments just after sunset, where the hustle of the city seemed to pause, and the sky became a canvas of colors.Emma was not just a dreamer; she was a doer. Her passion for environmental conservation had led her to create this garden, transforming a once barren space into a green haven amidst the concrete jungle. It was her belief that change begins with a single step, and this garden was hers.The garden was more than a collection of plants; it was a symbol of hope, a testament to the power of perseverance. Each sapling she had planted was a word, each blooming flower a sentence, and together, they told a story of resilience.This narrative exemplifies the use of descriptive language to paint a vivid picture in the reader's mind. It demonstrates how varied sentence structures create a rhythm that enhances the storytelling. Moreover, it reflects the seamless integration of ideas, a skill that the educational unit aims to instill in its students.In conclusion, the "People's Education Edition: English for Junior High School (Grade 8, Volume 2)" is not just a textbook; it's a guide to navigating the ocean of language learning. It equips students with the tools they need to chart their course, encouraging them to explore the depths of the English language and discover the treasures it holds. As learners embark on this voyage, they are reminded that the journey of language learning is continuous, and each step forward is a wave conquered in the sea of knowledge.。
八年级下册语文学海风暴RJ人教版答案20221. 1.下面加点字词注音全都正确的一项是() [单选题] *D.邑人(yì) 刘子骥(jì) 便要还家(yào)(正确答案)C.郡下(jùn) 黄发垂髫(táo) 阡陌交通(qiān mò)B.间隔(jiān)豁然开朗(huò) 怡然自乐(yí)A.叹惋(wǎn)林尽水源(yuán) 屋舍俨然(yǎn)答案解析:【解析】B项“间”应读jiàn,C项“髫”应读tiáo,D项“要”是通假字,同“邀”,应读yāo。
2. 15.成语皆言简意赅,许多成语都语出有典,如成语、就是出自本文。
[填空题]答出两个即可_________________________________答案解析:世外桃源无人问津豁然开朗3. 下面对本文内容的分析,不正确的一项是( ) *把选项和翻译都选出来A. 缘溪行,忘路之远近。
翻译:(有一天他)沿着溪水划船前行,忘了路程的远近。
B. 阡陌交通,鸡犬相闻。
(正确答案)翻译:乡村间的交通十分方便,(村落间)能听到鸡鸣狗叫的声音。
(正确答案)C. 问今是何世,乃不知有汉,无论魏晋。
翻译:(他们)问(渔人外面)现在是什么朝代,竟然不知道有过汉朝,更不必说魏晋了。
D. 此中人语云:“不足为外人道也。
”翻译:(临别时)村里人告诉(渔人)说:“(我们这个地方)不值得对外边的人说啊。
”答案解析:阡陌交通,鸡犬相闻:田间小路交错相通,鸡和狗的叫声到处都能听到到。
4. 10.下面句子不是省略句的一项是() [单选题] *A.黄发垂髫,并怡然自乐(正确答案)B.见渔人,乃大惊,问所从来C.及郡下,诣太守,说如此D.此人一一为具言所闻答案解析:B项应为“(桃花源中的人)见渔人,乃大惊,问(渔人)所从来”;C项应为“(渔人)及郡下,诣太守,说如此”;D项应为“此人一一为(桃花源中的人)具言所闻”。
学海风暴八年级下册物理RJ版2022答案1、19.有甲、乙两金属块,它们的质量之比为3:5,密度之比为5:7,则它们的体积之比是()[单选题] *A.3:7B.7:5C.5:3D.21:25(正确答案)2、40.寒冷冬天的早晨,思雨同学从家里到学校后,发现头发上有白花花的霜;进入教室后,过一会儿头发变湿了。
这里先后发生的物态变化是()[单选题] *A.凝固、汽化B.凝华、熔化(正确答案)C.凝华、升华D.凝固、液化3、11.小明正在家里练习弹吉他,下列有关吉他的说法正确的是()[单选题] *A.吉他发出的声音一定不是噪声B.吉他发出的声音是吉他弦振动产生的(正确答案)C.弹吉他时,用力越大,发出声音的音调越高D.弹吉他时,手按压吉他弦不同位置是为了改变响度4、64.为了揭示大自然的奥秘,无数科学家进行了不懈的探索。
下列说法错误的是()[单选题] *A.组成大自然的天体和微观粒子都在不停地运动,其中太阳是宇宙真正的中心(正确答案) B.汤姆孙发现了电子,从而揭示了原子是可以再分的C.卢瑟福最早提出了原子的核式结构模型D.近代科学家提出质子和中子都是由被称为夸克的更小粒子组成的5、16.为测量某种液体的密度,小明利用天平和量杯测量了液体和量杯的总质量m及液体的体积V,得到了几组数据并绘出了m﹣V图像。
下列说法正确的是()[单选题] *A.该液体密度为lg/cm3B.该液体密度为33g/cm3C.量杯质量为80gD.100cm3的该液体质量为80g(正确答案)6、小刚是一名初中生,他从一楼跑到三楼的过程中,克服自己重力所做的功最接近下面哪个值()[单选题]A.3JB.30JC.300JD.3000J(正确答案)7、58.哈勃望远镜使我们感受到宇宙的浩瀚,电子显微镜使我们认识到微观世界的深邃。
关于宇宙和粒子,下列说法错误的是()[单选题] *A.电子绕原子核运动与地球绕太阳运动相似B.用光年表示宇宙时间,用纳米量度分子大小(正确答案)C.宇宙是一个有层次的天体结构系统,它是有起源的、膨胀的和演化的D.固体、液体很难被压缩是因为分子间存在排斥力8、59.1911年,卢瑟福在α粒子散射实验的基础上,提出了原子核式结构模型。
八年级下册政治学海风暴试卷答案1、我国社会主义改造完成的历史意义有(? ? )①使我国的社会经济结构发生根本变化②我国的阶级关系发生了重要变化③进一步解放了我国的社会生产力④丰富和发展了马克思主义的科学社会主义理论[单选题] *A. ①②③B. ②③④C. ①③④D.①②③④(正确答案)2、本质和现象的关系()。
[单选题] *A.对立的B.对立统一的(正确答案)C.完全一致D.各不相干3、我国全面推进依法治国,总目标是()[单选题] *A.推动构建新型国际关系,推动构建人类命运共同体B.完善和发展中国特色社会主义制度、推进国家治理体系和治理能力现代化C.建设中国特色社会主义法治体系、建设社会主义法治国家(正确答案)D.建设一支听党指挥,能打胜仗,作风优良的人民军队,建设成为世界一流军队4、认识的基础是()。
[单选题] *A.经验B.科学理论C.实践(正确答案)D.学习书本知识5、第四课3单选题习近平新时代中国特色社会主义思想回答了(? ?)[单选题] *A.坚持和发展什么样的中国特色社会主义(正确答案)B.正确把握世界发展大势,应对全球共同挑战C.中国革命和建设的宝贵经验和正确思想D.中华民族站起来、富起来到强起来的飞跃6、新民主义革命反对的是()[单选题] *A.官僚主义、帝国主义、封建主义B.封建主义、官僚资本主义、帝国主义(正确答案)C.封建资本主义、帝国主义、官僚主义D.资本主义、封建主义、官僚主义7、中国共产党人的初心和使命是(? )[单选题] *A.自觉坚持党的领导和我国社会主义制度B.中国人民谋幸福,为中华民族谋复兴(正确答案)C.坚持并深入推进党的建设新的伟大工程D.推进中国特色社会主义伟大事业8、(? ? ?)是决定当代中国命运的关键一招,也是决定实现两个一百年奋斗目标,实现中华民族伟大复兴的关键一招。
[单选题] *A.改革开放(正确答案)B.对外开放C.解放思想D.实事求是9、75. 私营企业主的个人所得属于按劳分配。
八年级下册历史学海风暴答案20221、2.史载唐太宗时,有大臣奏请修复长城,太宗一笑置之。
太宗不修长城的理由是()[单选题] *A.唐初北方无边患B.长城已失去防御能力C.唐朝国力虚弱,无财力支持D.与各民族关系融洽(正确答案)2、14.唐太宗说:“其(夷狄)情与中夏不殊……四海可使如一家。
”下列史实中,与唐太宗直接相关并体现上述观念的是[单选题] *A.将文成公主嫁给松赞干布(正确答案)B.把金城公主嫁给吐蕃赞普C.设置驻藏大臣管理西藏D.设置伊犁将军管辖新疆3、66.下表显示了东汉中后期10个皇帝的即位年龄和寿命,与此密切相关的史实是()[单选题] *A.陈胜、吴广起义的爆发B.七国之乱的爆发C.外戚与宦官交替专权(正确答案)D.北方民族的内迁4、毛泽东曾经说过:“唐明皇(唐玄宗)不会做皇帝,前半辈会做,后半辈不会做。
”毛主席说“前半辈会做”是基于唐明皇统治前期的()[单选题] *A. 开皇之治B. 贞观之治C. 贞观遗风D. 开元盛世(正确答案)5、堪称当时世界之最,却加速民不聊生,王朝倾覆的宏大工程,除隋朝的大运河外,最为典型的是()[单选题] *A.都江堰B.秦长城(正确答案)C.唐长安D.明皇宫6、世界上迄今发现的古代第一部比较完备的成文法典中第282条规定,倘奴隶告其主人云:“你非吾之主人”,则此主人应证实其为自己的奴隶,而后其主人得割其耳。
该法典出自()[单选题] *A.古代埃及B.古巴比伦王国(正确答案)C.古代印度D.中国7、61.以下关于东汉的史实按时序排列正确的是()[单选题] *A.光武中兴——外戚宦官交替专权——黄巾起义——州牧割据(正确答案)B.州牧割据——光武中兴——外戚宦官交替专权——黄巾起义C.光武中兴——外戚宦官交替专权——州牧割据—黄巾起义D.黄巾起义——光武中兴——州牧割据——外戚宦官交替专权8、对赤壁之战中曹操战败的原因的分析,不正确的是()[单选题] *A.曹军自北方,不习水战B.骄傲自满,对孙、刘联军采用的战术未引起重视C.曹军疾疫流行,战斗力减弱D.天气环境(刮东风)使曹军失败(正确答案)9、潘老师为增强学生对唐朝中外交流历史的学习兴趣,和地理、电脑老师合作,根据史实设计了一套名为《神游大唐》的PRG(角色扮演)游戏。
《学海风暴》课外拓展提高二十四参考答案及解析1.D 2.B 【解析】由于线边上的中线为2则斜边为4.设一直角边例AB为x则另一直角边例BC为y。
由题意得∵在△ABC中根据勾股定理xy平方26①x平方y 平方16②.由①得x平方2xyy平方26.∵x平方y平方16。
∴2xy10解得xy5.∵S△ABC1/2xy。
∴S△ABC5/2.
3.A
4.D 【解析】∵△ABCD是矩形∴ADBC。
∵EFBF3∴EC8.∴EC
5.∴在△EFC中根据勾股定理得FC4.设AFx则在△ADC中8平方x平方x4平方。
解得AF5cm 5.A
6.4或12
7.2
8.75°【解析】∵AE平分∠BAD∴∠BAE∠EAD45°又知∠EAO15°∴∠OAB60°∵OAOB∴△BOA为等边三角形∴BABO ∵∠BAE45°∠ABC90°∴△BAE为等腰直角三角形∴BABE ∴BEBO∠EBO30°∠BOE∠BEO 此时∠BOE75°故答案为75°
9.4或【解析】解如图一所示AB是矩形较短边时∵矩形ABCD ∴OAODBD ∵OEED13 ∴可设OExED3x则OD2x ∵AE⊥BDAE ∴在Rt△OEA中x 平方平方2x平方∴x1 ∴BD4 当AB是矩形较长边时如图二所示∵OEED13 ∴设OEx则ED3x ∵OAOD ∴OA4x 在Rt△AOE中x平方平方4x平方∴x ∴BD8×8×故答案为4或10.20cm或22cm。
11.解如图所示连接BE。
∵四边形ABCD是矩形∴∠
A90°。
∵O为AC中点EO⊥BD∴在△EOB和△EOD 中EOEO∠EOB∠EODBOOD。
∴△EOB≌△EODSAS。
设AEx则EDEB4-x.∵在Rt三角形ABE 中根据勾股定理EB平方AE平方AB平方.即4-x平方x平方3平方.解得x.∴AE. 12.解:1证明:∵四边形ABCD是矩形. ∴DC//AB.∴∠DCA∠CAB. 又∵∠CAB∠EDC ∴AC//DE 2∵在△DEC和△AFB中:∠CAB∠EDC∠DEC∠AFBABDC. ∴△DEC≌△AFBAAS ∴ECFB∠ECD∠FBA。
∴EC//FB ∴四边形ABCD为平行四边形。