中考数学基础过关复习第五章三角形第1课时三角形的基本知识课件89.ppt

1、第1课时 三角形的基本知识中考考什么1.（2017北部湾）如图，ABC中，A=60，B=40，则C等于（）A.100 B.80 C.60 D.40BC2.(2017南宁良庆区模拟)一根长竹签切成四段，分别为3cm，5cm，7cm，9cm.从中任意选取三根首尾依次相接围成不同的三角形,则围成的三角形共有（）A.1个 B.2个 C.3个 D.4个A3.(2017南宁江南区模拟)如图，在ABC中，D，E分别为BC上两点，且BDDEEC，则图中面积相等的三角形有（）A.4对 B.5对 C.6对 D.7对C4.(2017南宁兴宁区模拟)如图所示，把一根铁丝折成图示形状后，ABDE，则BCD等于（）A.D

2、+BB.B-DC.180+D-BD.180+B-DD5.（2015北海）三角形三条中线的交点叫做三角形的（）A.内心 B.外心 C.中心 D.重心核心考点解读 三角形的分类1.三角形的边与角（1）三角形两边的和 第三边，三角形两边的差 第三边.（2）三角形三个内角的和等于 .（3）在同一个三角形中，小边对小角.大于小于大边对大角180 一般三角形的性质和大于固定没有2.三角形内外角关系（1）三角形的外角等于与它不相邻的两个内角的 .（2）三角形的外角 任何一个和它不相邻的内角.3.三角形的稳定性三角形形状是 的，只要三角形三边固定，三角形的形状和大小就确定不变了，三角形的这个性质叫做三角形的稳

3、定性.四边形 稳定性.温馨提示三角形的角平分线、中线、高线是线段.三角形三条中线的交点叫做三角形的重心；三条角平分线的交点叫做三角形的内心；三条高的交点叫做三角形的垂心.特别区分垂直平分线是直线不是线段.两边中点平行于一半2.三角形的中位线（1）中位线：连接三角形 的线段叫做三角形的中位线.（2）中位线定理：三角形的中位线 第三边，并且等于第三边的 .怎么考 三角形的三边关系样题1 已知三角形两边的长分别是5和8，则此三角形第三边的长可能是下列的（）A.3 B.4 C.13 D.14B解析先根据三角形的三边关系求出x的取值范围，再求出符合条件的x的值即可.设此三角形第三边的长为x，则8-5x8

4、+5，即3x13.只有选项B符合题意.变式训练1.（2016河池）下列长度的三条线段不能组成三角形的是（）A.5,5,10 B.4,5,6 C.4,4,4 D.3,4,5A2.下列长度的三根小木棒能构成三角形的是（）A.2cm，3cm，5cm B.7cm，4cm，2cm C.3cm，4cm，8cm D.3cm，3cm，4cmD3.(2017南宁兴宁区模拟)在ABC中，三边长分别为a，b，c，且abc，若b=8，c=3，则a的取值范围是（）A.3a8 B.5a11 C.6a10 D.8a11D 三角形的角的关系样题2 如图，在ABC中，CD是ACB的平分线，A=80，ACB=60，则BDC的度数

5、为 。110解析本题根据“三角形的一个外角等于和它不相邻的两个内角的和”可解决.CD是ACB的平分线，ACB=60，ACD=30.A=80，BDC=A+ACD=110.变式训练4.（2016百色）三角形的内角和等于（）A.90 B.180 C.300 D.3605.（2016贵港）在ABC中，若A=95，B=40，则C的度数为（）A.35 B.40 C.45 D.50BC6.(2017南宁西乡塘区模拟)如图，直线ab，一块含60角的直角三角板ABC（A=60）按如图所示放置.若1=55，则2的度数为（）A.105 B.110 C.115 D.120C 三角形中重要线段的运用样题3 如图，在AB

6、C中，D，E分别是边AC，AB的中点，连接BD.若BD平分ABC，则下列结论错误的是（）A.BC2BE B.AEDAC.BC2AD D.BDACC 解析根据D，E分别是边AC，AB的中点，得出DE是ABC的中位线，所以DEBC且BC=2DE；又BD平分ABC，所以CBD=DBE=BDE，所以BE=DE=AE，所以AB=2DE，所以AB=BC，则BC=2BE，A=C=EDA，BDAC.变式训练7.(2017南宁邕宁区模拟)如图，AD是ABC中BAC的角平分线，DEAB于点E，SABC=7，DE=2，AB=4，则AC长是（）A.3 B.4 C.6 D.5A8.（20165来宾）如图，在ABC中，A

7、B=4，BC=6，DE、DF是ABC的中位线，则四边形BEDF的周长是（）A.5 B.7 C.8 D.10D9.如图，在RtABC中，B=90，A=40，AC的垂直平分线MN与AB相交于D点，则BCD的度数是 .10补充练习一、完形填空(共15小题；每小题1分，满分15分)阅读下面短文，掌握其大意，然后从每题所给的A、B、C、D四个选项中选出最佳选项。Life is full of the unexpected._1 1_a cold winter afternoon，a man saw an old lady standing by her expensive car and clearly

8、 she needed help.So he stopped and _2 2_ his old truck.“Is he going to hurt me?He doesnt look safe，”the old lady was _3 3_(B B)1.1.A.In BOn CAt DUnder(D D)2.2.A.went off Bturned off Ctook off Dgot off(C C)3.3.A.glad Bexcited Cworried Dsurprised The man could see that she was afraid，so he said in his

9、 friendliest_4 4_，“Im here to help you，madam.Why dont you_5 5_ in the car where its warm？_6 6_，my name is Ted Johnson.”Ted quickly fixed the car and the lady thanked him.Then she asked _7 7_ she should pay him.(A A)4.4.A.voice Bsound Cnoise Dlook(A A)5.5.A.wait Bto wait Cwaited Dwaits(D D)6.6.A.In a

10、 way BOn my way CUnder the way DBy the way(B B)7.7.A.how many Bhow much Chow far Dhow often But Ted wanted_8 8_ money.He was just giving a hand to someone in trouble._9 9_ was normal for him to do such a thing like that.He said，“If you really want to repay(报答)me，next time you see someone in need，thi

11、nk of me and help them.”(B B)8.8.A.not Bno Csome Dany(C C)9.9.A.This BThat CIt DThey After saying goodbye，the lady continued down the road until she reached a small_1010_where she decided to stop for something to eat.As the pretty waitress took her order，the lady noticed she was _1111_ eight months

12、pregnant(怀孕)The waitress looked tired and weak，_1212_she was very kind.As the lady was going to pay the$10 bill，she remembered Teds words.(A A)10.10.A.restaurant Bbookstore Ccinema Dlibrary(C C)11.11.A.mostly Bhardly Cnearly Dseldom(B B)12.12.A.so Bbut Cor Dthough After the lady was gone，the waitres

13、s saw a small note on the table.It said，“Somebody once helped me the way Im helping you.Continue being kind to other people.”Under the note were five _1313_ dollars.The waitress was_1414_ excited that she called her husband to tell him the news，“TedTed Johnson my dear youre not going to believe _151

14、5_ just happened”(A A)13.13.A.hundred Bhundreds Chundred of Dhundreds of(D D)14.14.A.too Bvery Csuch Dso(C C)15.15.A.how Bwhen Cwhat Dwhy二、阅读理解(共15小题；每小题2分，满分30分)阅读下面四篇短文，从每题所给的A、B、C、D四个选项中选出最佳选项。A A(20172017广东中考改编)(C C)16.16.The World Poetry Day is on _ AAugust 28th BMarch 3rd CMarch 21st DAugust 2

15、8th(D D)17.17.The purpose of the World Poetry Day is _Ato encourage the British to write poemsBto teach children how to read and write poemsCto raise money for the poets from all over the worldDto help people to read，write and teach poems better(A A)18.18.The rules for the competition include the fo

16、llowing EXCEPT_Athat poets can write poems in any languageBthat poets must use their unpublished poemsCthat poems cant be written on the subject of violence or drugsDthat poems cant be taken back after the competitionB B Sports can help you keep fit and close to nature.However，whether you are on the

17、 mountains，in the waves，or on the grassland，you should realize that sport you choose might have great influence on the environment.Some sports are resourcehungryGolf，as you may know，eats up not only large areas of countryside，but also lots of water.Besides，huge amounts of energy are used to keep its

18、 courses(球场)in good condition.This causes major environmental changes.For example，in the dry places of Portugal and Spain，golf is often held responsible for(为承担责任)serious water shortage(短缺)in some local areas.There are many environmentfriendly sports.Power walking is one of them that you could take

19、up today.You dont need any special equipment except a good pair of shoes，and you dont have to worry about resources and your purse.Simple and free，power walking can also help you stay healthy.If you walk regularly，it will be good for your heart.Experts say that 20 minutes of power walking daily can

20、make you feel less anxious，sleep well and keep thin.Whatever sport you take up，you can make it greener than by using environmentfriendly equipment and buying products made from recycled materials.But the final goal should be“green gyms”They are better replacements(替代)for traditional health clubs and

21、 modern sports centers.Members of green gyms play sports outdoors，in the countryside or other open spaces.There is no special requirement for you to start your membership(会员身份)And best of all，its free.(A A)19.19.Which of following does the author most probably support according to the passage?ABicyc

22、ling around the lake.BCar racing on the road.CPlaying basketball in a gym.DSwimming in a sports centre.(D D)20.20.What does the underlined phrase“resourcehungry”in this passage mean in Chinese?A广为流行的 B亲近自然的C低成本的 D耗费资源的(C C)21.21.The author uses power walking as an example mainly because_Ait is an ou

23、tdoor sport Bit is loved by many peopleCit uses fewer recourses Dit is supported by experts(B B)22.22.The author writes the passage to _Ashow us disadvantages of golfBurge us to take part in green sportsCexplain the major sports influence of popular sportsDdiscuss different kinds of environmentfrien

24、dly sport C C Lao She wrote Teahouse in 1957.The play shows the audience life in China between 1898 and 1945.It takes place in a teahouse in old Beijing and it tells us the story of Wang Lifa and his customers.It asks us to see the teahouse as the centre of the neighbourhood.Finally，it says goodbye

25、to old Beijing and its people.The story starts in 1898 during the Qing Dynasty.It continues in 1916，and finally，it brings the audience to the end of the AntiJapanese War in 1945.After the war，Wang loses the teahouse and he dies.Lao She was born in Beijing in 1899.His parents sent him to the Teachers

26、 School in Beijing and he learned to teach.From 1924 to 1929 he taught Chinese to the English in London.He wrote many plays，novels and short stories.He was named a“Peoples Artist”and a“Great Master of Language”He was one of the greatest Chinese writers of the 20th century.In Lao Shes Teahouse today，

27、waiters bring tea to the customers and sell them delicious Chinese food.If you like Beijing Opera，folk music，acrobatics or magic shows，you can enjoy them in the teahouse.Lao Shes Teahouse gives a wonderful welcome to everyone from China and from all over the world.(B B)23.23.Whats the main idea of P

28、aragraph 4?ALao She.BLao Shes Teahouse.CThe story of Teahouse.DThe play Teahouse.(D D)24.24.How many years of life in China is shown in the play Teahouse?A57 years.B45 years.C98 years.D47 years.(A A)25.25.Lao She was all of the following except _Aa boss of TeahouseBa Peoples ArtistCa Great Master of

29、 Language Done of the greatest Chinese writers of the 20th century(C C)26.26.Who were welcome to Lao Shes Teahouse today?AOnly Chinese customers.BOnly foreign customers.CEvery customer from home and abroad.DOnly Beijing Opera audience.D DSpecial Bridges Help Animals Cross the RoadSpecial Bridges Hel

30、p Animals Cross the RoadReported by Sheila Carrick Why did the chicken cross the road?To get to the other side.Most people know this joke.But recently，some people have been much more worried about how the grizzly bear(灰熊)and mountain lion can cross the road.“Millions of animals die each year on US r

31、oads，”the Federal Highway Administration reports.In fact，only about 80 ocelots，an endangered wild cat，exist in the US today.The main reason?Road kill.“Ecopassages(生态通道)”may help animals cross the road without being hit by cars.They are paths both over and under roads.“These ecopassages can be extrem

32、ely useful，so that wildlife can avoid road accidents，”said Jodi Hilty of the Wildlife Protection Society.But do animals actually use the ecopassages?The answer is yes.Paul Beier of Northern Arizona University found foot marks left by mountain lions on an ecopassage that went under a highway.This sho

33、wed that the lions used the passage.Builders of ecopassages try to make them look like a natural part of an area by planting trees on and around them.Animals seem to be catching on.Animals as different as salamanders(火蜥蜴)and grizzly bears are using the bridges and underpasses.The next time you visit

34、 a park or drive through an area with a lot of wildlife，look around.You might see an animal overpass!(D D)27.27.The writer uses the example of“ocelots”to show that _Awild animals have become more dangerousBthe driving conditions have improved greatlyCthe measure for protecting wildlife fails to work

35、Dan increasing number of animals are killed in road accidents(D D)28.28.From the passage，we know an ecopassage is _Aan underground path for carsBa fence built for the safety of the areaCa bridge for animals to get over a river Da path for animals to cross the road(B B)29.29.When the writer says that

36、“Animals seem to be catching on”，he means _Aanimals begin to realize the dangers on the road Banimals begin to learn to use ecopassagesCanimals are crossing the road in groupsDanimals are increasing in number(D D)30.30.The writer asks visitors and drivers to look around when travelling because_Awild

37、 animals may attack cars Bwild animals may jam the roadCthey may see wild animals in the park Dthey may see wild animals on ecopassages三、词汇运用(共15小题；每小题1分，满分15分)A用方框中所给词语的适当形式填空。每词限用一次。3131Mr Li has made a_decisiondecision_ to travel to Beijing.3232The school_providesprovides_ the students with delic

38、ious food every day.3333He just sat_inin_silencesilence_ and didnt say any words.3434I have been to several_EuropeanEuropean_ countries，such as England and France.3535You cant go _acrossacross_ the street when the traffic lights turn red.B根据短文内容和所给中文提示，在空白处写出单词的正确形式。每空限填一词。It is 8：30 am at the Cheng

39、du Research Base.Lin Wei，a panda keepers，is preparing the milk for the baby pandas 36.36._breakfastbreakfast_(早餐)At 9：00 am，she finds that most of the babies are already 37.37._awakeawake_(醒着的)and hungry.When the babies see the keepers，they run over with excitement，and some of them even 38.38._walkw

40、alk_(行走)into their friends and fall over!Theyre so cute and lovely.Lin Wei takes care of them like theyre her 39.39._ownown_(自己的)babies.She washes，feeds and plays with them every day.Pandas do not have many babies，maybe only one every two years.The babies often 40.40._diedie_(死亡)from illnesses and d

41、o not live very long.Adult pandas spend more than 12 hours a day eating about 10 kilos of bamboo.Many years ago，there were a lot more bamboo forests and pandas in China.But now pandas are in great 41.41._dangerdanger_(危险)People cut down many bamboo trees so they are losing their homes.There are abou

42、t 1，590 42.42._wildwild_(野生的)pandas living in the forests in Sichuan，Shaanxi and Gansu provinces.Another 200 or so live in zoos or research centres in China and other countries.Its a 43.43._pitypity_(遗憾)that many people dont know that.So the government has set up an education programme in Chengdu.It

43、 teaches children in cities about p a n d a s，and tells them about the 44.44._importanceimportance_(重要性)of saving the pandas.But t e a c h i n g c h i l d r e n i s o n e w a y t o h e l p 45.45._protectprotect_(保护)environment and save pandas.The Chinese government is also planting more bamboo trees

44、 so there will be more forests for pandas to live in.We all hope that in the future there will be a lot more pandas than now.四、语法填空(共10小题；每小题1分，满分10分)阅读下面短文，在空白处填入一个适当的词，或填入括号中所给单词的正确形式。Some people still live in their home town.However，others may only visit 46.46._itit_once or twice a year.Millions

45、of Chinese leave the countryside 47.47._toto_searchsearch_(search)for work in the cities.Among these is Hua Xing.He 48.48._hashas_livedlived_(live)in Wenzhou for the last 13 years.With a hard job 49.49._inin_ a factory，he seldom visits his home town.“I havent been back 50.50._forfor_ three years.Its

46、a shame，”he says.51 51_DevelopmentsDevelopments_(develop)have been good in Hua Xings home town since 2002，for example，new roads 52.52._havehave_appearedappeared_(appear)A new school 53.53._hashas_beenbeen_builtbuilt_(build)However，some things will never change in his home town.The big old tree is st

47、ill beside the playground.Children in his time 54.54._usuallyusually_(usual)liked to play together under it.It was 55.55._suchsuch_ happy childhood.五、(20172017邵阳中考)任务型阅读(共5小题；每小题1分，满分5分)阅读下列短文，在空白处(5660)填入与短文内容相符的信息，完成阅读摘记。Maciek Czastka was born in Lodz，Poland.He came to China several years ago.So

48、far，he has been working in Chengdu for three years.“The Belt and Road Initiative(一带一路的倡议)is meaningful，”he said.“Thanks to it，we are offered more chances.”The most powerful support for Chengdu to thrive(兴盛)along the Belt and Road is the ChengduEurope express railway(高速铁路)It provides direct train ser

49、vices between Chengdu and the city of Lodz.Because of the express railway，trains can bring things from China to Europe.At the same time，they can bring back European food，wine，meat and so on.In 2016，a total of 460 trains ran between Chengdu and Europe.The number is expected to grow to 1，000 this year

50、.Since the ChengduLodz express railway was opened.Chengdu，together with other cities in west China，has developed close trade ties with the European country.Poland is one of the largest apple producers in Europe.Czastkas company helps farmers in Poland sell their apples to China.More and more Europea