课时作业(十九)
高中英语课时作业十九Unit6Design北师大版必修2
课时作业(十九) Unit 6 DesignⅠ.用适当的介词或连词填空1．We didn’t go to bed twelve last night.答案：until2．There is a blackboard the front of our classroom.答案：in3．My father will be back three days.答案：in4．There is a bridge the river.We can go across the river easily.答案：over5．The sun sinks the horizon.The night falls.答案：below6．They walked the playground and came to the dining room.答案：across7．I walked the forest，tired and hungry.答案：through8．He is busy packing up because he will leave Shanghai tomorrow.答案：for9．The window is well the tree.So you can see the garden clearly.答案：above10． Mary came to study，she has made much progress in Chinese.答案：SinceⅡ.完成句子1．— (从什么时候开始) has Jack been addicted to computer games?—2014，I suppose.答案：Since when2．We (对……很恼火) his mistake，because we have emphasized this for several times.答案：are very annoyed at3．I have already made a decision (对……采取什么态度) this matter.答案：what attitude to adopt to4．It is unbelievable that Mr Lucas leads a simple life (尽管他很富有)．答案：despite his great wealth5．This shop will be closed for repairs (在另行通知前)．答案： until further notice6．Some students often listen to music (课间) to refreshthemselves.答案：between classes7．My uncle (住在) 103 Chaoyang Street in Beijing.His flat is (在10楼)．答案：lives at；on the tenth floor8．The accident is reported to have occurred (在二月份第一个星期日)．答案：on the first Sunday in February9．Hong Kong is (在中国南部)，and Macao is (在香港西面)．答案：in the south of China；to the west of Hong Kong10．Fred entered without knocking and，very out of breath， (颓然坐在椅子上)．答案：sank into a chairⅢ.用适当的关系代词填空1．The place interested me most was the Children’s Palace.答案：which/that2．That is the day I’ll never forget.答案：which/that3．The factory we’ll visit next week is not far from here.答案：which/that4．Is there anyone in your class father is in the country?答案：whose5．The foreign guests liked the children and their shows they saw in thekindergarten.答案：that6．It was in the small house was built with stones that he spent hischildhood.答案：which7．The girl name was Diana sat next me.答案：whose8．I’ve read all the books you gave me.答案：that9．I am going to meet Tom they say is a good boy.答案：who10．We went to see our teacher husband lost his life in the earthquake.答案：whoseⅣ.用定语从句完成句子1．The professor mentioned some poets and poems (他们不为我们所知) in his lecture.答案：that were unknown to us2．We’l l call on a man (我认为他能给我们很好的意见)．答案：who I believe can give us very good advice3．When I got to New York，I had to attend a school for students (他们的母语不是英语)．答案：whose first language was not English4．He put forward a good idea (它给了我们希望)．答案：that gave us hope5．Thanks to the timely treatment，the patient (人们都认为他会死去) slowly recovered.答案：who people all thought would die6．Tom is the one of the boys (守时的)．答案：who is on time7．The very hotel (你正想到的)，my dear，is just a bittoo expensive for us，I am afraid.答案：that you are thinking of8. Because of my poor memory，all (你所告诉我的) has beenforgotten.答案：that you told meⅤ.阅读理解A 15yearold boy planned to put a ball covered with gasoline (汽油) into hismouth and set it on fire.He would film the dangerous action and put it on YouTube.And，he hoped to become famous on the Internet.But things didn’t go the way he imagined.His clothing caught fire，and he was rushed to the hospital with serious burns on his body.YouTube hosts millions of videos of people attempting dangerous actions.Many of them are by kids and young adults.Some experts say that by hosting these videos，YouTube encourages young viewers to take deadly (致命的) risks.Research by the Centers for Disease Control and Prevention shows that more than 180,000 Americans die from accidental injuries each year.That’s one person every three minu tes.More than 14,000 of those killed are kids under the age of 19.Is YouTube to blame?People have always found it interesting to watch others try risky things.Audiences love these kinds of things.Some of the earliest Greek comedies had characters followed by wild animals and knocking into walls.Now，in the age of the Internet，anyone with a camera and a YouTube account (账户) can create this kind of “fun”．Many viewers，especially teenagers，are influenced by what they see and want to try it themselves.“YouTube h as taken the playing in the neighborhood to a worldwide level，” says Clair Mellenthin，a researcher from the Centers.“People are greatly influenced，because now we can see what others are doing around the world.”Supporters of YouTube argue that it isn’t YouTube’s responsibility to examine its content (内容)．“Parents should be the ones to make sure that kids are behaving safely，” they say.In fact，YouTube has a rule on content.For example，dangerous activities that have a risk of serious physical harm or death are not allowed.Staff of YouTube carefully watch the website 24 hours a day，looking for videos that are against their rules.But is this enough?语篇解读本文是议论文。
高中化学选择性必修1课时作业19
B．①③④②
C．③④②①
D．③①②④
新教材•化学(RJ) 选择性必修1
新教材·化学（RJ） 选择性必修1
解析：利用原电池的形成和工作原理解决问题。在外电路中，电流从正
极流向负极，则①作原电池的负极，②作正极，故金属活动性①>②；活动
性相对较差的金属作原电池的正极，故金属活动性①>③；有气泡产生的电 极发生的反应为 2H＋＋2e－===H2↑，为原电池的正极，故金属活动性④>②； 质量减少的电极发生氧化反应生成金属离子而溶解，为负极，故金属活动性
新教材•化学(RJ) 选择性必修1
新教材·化学（RJ） 选择性必修1
6．用铜片、银片、Cu(NO3)2 溶液、AgNO3 溶液、导线和盐桥(装有琼脂-KNO3
的 U 形管)构成一个原电池。以下有关该原电池的叙述正确的是( C )
①在外电路中，电流由铜电极流向银电极 ②正极反应为 Ag＋＋e－===Ag
12．(双选)一种铁空气电池的电池反应为：2Fe＋O2＋2H2O===2Fe(OH)2， 原理如图所示，下列有关该电池的说法正确的是( AC )
A．b 极为电池正极，发生还原反应 B．当电路中转移 0.2 mol 电子时，消耗 1.12 L O2 C．a 极的电极反应式为：Fe－2e－＋2OH－===Fe(OH)2 D．电子由 a 极经负载流向 b 极，再经过 NaOH 溶液回到 a 极
新教材•化学(RJ) 选择性必修1
4．下列叙述中正确的是( D )
新教材·化学（RJ） 选择性必修1
A．原电池的负极得电子，发生还原反应
B．原电池中较活泼的金属作正极
C．原电池中的电极一定要由两种不同的金属组成
D．原电池中发生氧化反应的电极是负极
高中生物学必修1课时作业(十九)
6．阳台菜园成为城市居民的一种时尚装扮，同时可为居民提
供新鲜蔬菜。下列有关说法正确的是( A )
A．阳台内的蔬菜进行光合作用利用的光主要来自自然光 B．在阴雨天可适当提高阳台蔬菜所处环境的温度以避免减产 C．晚上增施农家肥可提高CO2浓度，促进暗反应的进行 D．蔬菜中的叶绿素对光的吸收效率与光的波长呈正相关
(2) 当CO2浓度低于0.06%时，二氧化碳浓度是限制光合作用速 率的主要因素，二氧化碳参与光合作用暗反应中二氧化碳的固定 并产生三碳化合物，即暗反应中三碳化合物(C3)的生成速率限制 了光合作用速率。
(3) 与20 ℃相比，温度为10 ℃时，增加CO2浓度对提高光合作 用速率的效果不显著，原因是10 ℃时酶活性低。
③绘制图示曲线的数据__不__能____(填“能”或“不能”)直接测 量，原因是___图__示__反__映__的__是__总__光__合__速__率__，__而__有__光__时__测__得__的__是__净__ _光__合__速__率__(_合__理__即__可__)_____。
解析：(1) 分析曲线图可知，本实验的自变量是温度和CO2浓度。 由实验结果可知，四种温度相比，30 ℃时比较适宜，因此该作物 光合作用相关酶活性的最适温度在20 ℃～40 ℃之间。
解析：a～b段有光照，容器中绿色植物能进行光合作用，在 类囊体膜上进行的光反应消耗ADP产生ATP，在叶绿体基质中进 行的暗反应消耗ATP产生ADP，因此叶绿体中 ADP从基质向类囊 体膜运输，A 正确；
由乙图可知，前30 min平均净光合速率是(1 680－180)÷30＝ 50(ppm CO2/min)，平均呼吸速率是(600－180 )÷30＝14(ppm CO2/min)，因此，容器中绿色植物前30 min平均真光合速率为50 ＋14＝64(ppm CO2/min)，B错误；。
人教版英语必修一课时作业 19课
课时作业(十九)Unit 5Section ⅢLearning about Language & Using LanguageⅠ.单句语法填空1．The driver narrowly escaped being_killed (kill) in the traffic accident.2．Though he has met with many difficulties over the past two years, he is still hopeful (hope)．3．The first time I visited (visit) that land, I decided to settle there.4．It is the fifth time that the students in Trinity College have_visited (visit) our school.5．Now their peace talks have reached a key stage where one side must give in to the other.6．A large number of blankets (blanket) and clothes have been collected for the victims of the earthquake.7．That man is rather cruel and he is well known for his cruelty (cruel) in this village.8．As an educated (educate) man, Mr Wang acts properly in almost everywhere.9．When a person is in trouble, talking with others often helps him feel better.10．The boss decided to give a reward to him for his positive attitude towards work.Ⅱ.阅读理解AHo w Grandpa Tata Caught a Ginormous Fish w ithout a HookBy Dhan ReddyRating(等级)：4.6 out of 5 starsMany children are lucky enough to go fishing. The luckiest ones get to go fishing with their grandpas! In this story, Dinesh and his grandpa go in search of a really big fish and catch the world's biggest fish with nothing but a piglet(小猪)! This book is a funny story ofgoing out and getting what you want—if you're willing to go beyond what others do.MerelyBy Cate DavisRating：4.5 out of 5 starsBorn in the Kalahari Desert in Africa, Merely the Meerkat is the only child of her mother, Mernie, who teaches her to keep an open heart, to be kind, and to look for the best in others. But Merely is unluckily taken from her home and family, along with many other animals, and transported across the ocean to an American zoo where her young life changes forever.The Way Things Ne v er WereBy Norman H. FinkelsteinRating：4.6 out of 5 starsIt seems like kids are always hearing stories about America in the “good old days.”But, in fact, the 1950s and 1960s were not as carefree(无忧无虑的) as they sometimes seem. Through interesting stories, advertisements, facts and photographs, Norman H. Finkelstein invites people of all ages to decide for themselves.Silent Days, Silent DreamsBy Allen SayRating: 4.8 out of 5 starsThis picture book tells the story of James Castle, an artist who grew up unloved by his family and community because of his deafness. This book is a story as much about acceptance and understanding as it is about perseverance(坚持)．【语篇解读】本文是应用文。
课时作业19电解池、金属的腐蚀与防护
课时作业(十九)一、选择题1．(2012·山东省模拟考试)下列有关金属腐蚀与防护的说法正确的是()A．黄铜(铜锌合金)制作的铜锣易产生铜绿B．镀锡铁制品和镀锌铁制品的镀层破损时，镀锡铁中铁的腐蚀速率更快C．在轮船船体四周镶嵌锌块保护船体不受腐蚀的方法叫阳极电化学保护法D．不锈钢有较强的抗腐蚀能力是因为在钢铁表面镀上了铬答案 B2．(2012·湖北省孝感市统一考试)下列有关电化学装置完全正确的是()答案 C3．(2012·山东省模拟考试)现将氯化铝溶液蒸干灼烧并熔融后用铂电极进行电解，下列有关电极产物的判断正确的()A．阴极产物是氢气B．阳极产物是氧气C．阴极产物是铝和氧气D．阳极产物只有氯气答案 B4．(2012·北京东城)认真观察下列几个装置示意图，有关叙述正确的是()A．装置①中阳极上析出红色固体B．装置②中a与电源的负极相连，b与电源的正极相连C．装置③的待镀铁制品应与电源正极相连D．装置④的a为电源的正极，b为电源的负极答案 B5．(2012·福建省四地六校联考)为使反应Cu ＋2H2O===Cu(OH)2＋H2↑能够发生，下列设计方案正确的是()A．用铜片作负极，石墨电极作正极，氯化钠溶液为电解质溶液构成原电池B．用铜片作电极，外接直流电源电解硫酸铜溶液C．用铜片作阳极，铁片作阴极，电解硫酸钠溶液D．用铜片作阴、阳电极，电解稀硫酸答案 C6．(2012·济南市质量调研)某溶液中含有两种溶质NaCl和H2SO4，它们的物质的量之比为3：1。
滴入几滴紫色石蕊溶液后，用石墨作电极电解该混合溶液，根据电极产物，电解过程可明显分为三个阶段。
下列叙述中不正确的是() A．阴极自始至终只产生H2B．电解过程中，溶液颜色呈现红色→紫色→蓝色的变化C．电解过程中，Na＋和SO2－4的物质的量浓度保持不变D．第一阶段中阴、阳两极产生的气体混合引燃后，恰好完全反应得到HCl解析由离子放电顺序并结合离子的数量，此电解的三个阶段具体情况如下答案 C7. 以Pt为电极，电解含有0.10 mol M＋和0.10 mol N3＋(M＋、N3＋均为金属阳离子)的溶液，阴极析出金属单质或气体的总物质的量(y)与导线中通过电子的物质的量(x)的关系如图。
【备战2014高考化学】课时作业19电解池 金属的腐蚀与防护
课时作业(十九)一、选择题1．(2012·山东省模拟考试)下列有关金属腐蚀与防护的说法正确的是() A．黄铜(铜锌合金)制作的铜锣易产生铜绿B．镀锡铁制品和镀锌铁制品的镀层破损时，镀锡铁中铁的腐蚀速率更快C．在轮船船体四周镶嵌锌块保护船体不受腐蚀的方法叫阳极电化学保护法D．不锈钢有较强的抗腐蚀能力是因为在钢铁表面镀上了铬答案 B解析铜锌合金在空气中可组成原电池，铜为正极得到保护，不易被腐蚀，A项错误；镀锡铁与镀锌铁都可以组成原电池，由于铁的活泼性强于锡，铁为负极加快其腐蚀，而镀锌铁中铁为正极得到保护，B项正确；C中的方法叫牺牲阳极的阴极保护法，C项错误。
2．(2012·湖北省孝感市统一考试)下列有关电化学装置完全正确的是()解析电解精炼铜时，应该用粗铜作阳极，精铜作阴极，故A项错误。
铁上镀银时，应该用银作阳极，铁作阴极，故B项错误。
C是外接电源的阴极保护法，正确。
铜锌原电池中，锌应插入硫酸锌溶液中，铜应插入硫酸铜溶液中，故D项错误。
3．(2012·山东省模拟考试)现将氯化铝溶液蒸干灼烧并熔融后用铂电极进行电解，下列有关电极产物的判断正确的是() A．阴极产物是氢气B．阳极产物是氧气C．阴极产物是铝和氧气D．阳极产物只有氯气答案 B解析将氯化铝溶液蒸干灼烧得到Al2O3，电解熔融的Al2O3，阳极为O2－放电，阳极产物为氧气；阴极为Al3＋放电，阴极产物为Al。
4．(2012·北京东城)认真观察下列几个装置示意图，有关叙述正确的是()A．装置①中阳极上析出红色固体B．装置②中a与电源的负极相连，b与电源的正极相连C．装置③的待镀铁制品应与电源正极相连D．装置④的a为电源的正极，b为电源的负极答案 B解析阳极发生氧化反应，不能析出铜，应放出氯气，A项错误；电解熔融氯化钠，从图中看出a极上析出钠，为阴极，应与电源的负极相连，b极放出氯气，应与电源的正极相连，B项正确；铁制品上镀铜，铁制品应在阴极，与电源负极相连，C项错误；为了保护钢闸门，应将其与电源的负极相连，D项错误。
【初中化学】人教版九年级下册课时作业（十九） ［课题1 第2课时 复分解反应］(练习题)
人教版九年级下册课时作业（十九）［课题1 第2课时复分解反应］(407)1.请写出下列变化的化学方程式。
(1)硫酸铜溶液和氯化钡溶液反应：。
(2)在稀盐酸中滴加氢氧化钠溶液：。
2.X是常见的碳酸盐，可发生如图所示的变化，部分生成物省略。
根据图示回答问题。
(1)C的化学式是。
(2)写出图中①反应的化学方程式：，该反应的基本类型是。
3.判断复分解反应能否发生，不必考虑的是（）A.是否有沉淀生成B.是否有气体生成C.是否有水生成D.金属的活动性顺序4.下列关于物质的分类，错误的是（）A.氢氧化钠、纯碱都是碱B.碘酒、生理盐水都属于混合物C.水、氧化铁都是氧化物D.硫酸、硝酸都是酸5.下列物质间不能发生复分解反应的是（）A.碳酸钠溶液和氯化钙溶液B.氢氧化钠溶液和氯化钾溶液C.碳酸钾溶液和盐酸D.硫酸铜溶液和氯化钡溶液6.在“P+Q⟶盐和水”的反应中，物质P和Q不可能是（）A.HCl、Ca(OH)2B.SO2、NaOHC.Fe2O3、H2SO4D.H2SO4、ZnCl27.下列物质间的转化不能一步完成的是（）A.KNO3→NaNO3B.Mg→MgOC.Na2CO3→NaOHD.H2O→H28.将下列各组物质放入足量的水中，充分搅拌后，得到无色溶液的是（）A.HNO3和FeCl3B.NaOH和HClC.BaCl2和Na2SO4D.KOH和CuSO49.下列试剂能一次鉴别出稀盐酸、澄清石灰水、氢氧化钠溶液的是（）A.紫色石蕊溶液B.酚酞溶液C.碳酸钙粉末D.碳酸钠溶液10.按下表进行实验，有关说法及分析错误的是（）A.①有蓝色沉淀B.②反应的化学方程式为：CuSO+BaCl2=BaSO4↓+CuCl24C.两个反应都属于复分解反应D.只要有沉淀生成的反应就属于复分解反应11.按照物质的类别书写下列物质的化学式(任写一个)。
①金属单质：。
②非金属单质：。
③金属氧化物：。
④非金属氧化物：。
⑤酸：。
⑥碱：。
⑦盐：。
高中英语复习提升-课时作业(十九)
课时作业(十九)必修④Unit 4Body languageⅠ.阅读理解A[2019·贵阳市期末检测]You try to keep your eyes wide open while watching a basketball match or a wonderful firework show in case you might miss something exciting in just the blink of an eye. But in fact, humans blink about 15 times per minute on average. Have you ever missed anything because you blinked? Probably not. Why is that?According to a new study published in the journal Current Biology in September, our brain has the ability to skip the temporary darkness when we blink. It can keep visual information for a short period of time and then put it together to form an image without interruption.In order to understand how this works, a group of scientists at the German Primate Center and the University Medical Center Göttingen in Germany conducted an experiment. In the study, the participants were asked to look at patterns on a screen whose direction could be interpreted in different ways, such as horizontally(水平地) or vertically(垂直地). When one pattern was about to disappear and the next one was about to come, the participants had to indicate the direction that the next pattern would appear.The researchers found that when the directions of two patterns didn't match, the area in our brain which is responsible for visual memory was activated. This same area showed less activity when two patterns were in the same direction.“The medial prefrontal cortex (额叶皮层) adjusts current visual information with previously obtained information, and thus enables us to perceive the world with more stability, even when we briefly close our eyes to blink，” Caspar Schwiedrzik explained in Science Daily. He is the first author of the study and also a scientist at the German Primate Center.1．We don't miss anything when blinking because our brain can ________.A．deal with the missing imageB．remember all that we seeC．imagine what our eyes missD．put our pieces of memory together2．What does the underlined word “it” in Paragraph 2 refer to?A．Our brain.B．Visual information.C．Current Biology. D．The temporary darkness.3．What do we know about the experiment?A．The two patterns appear at the same time.B．Visual memory can be more activated by similarity.C．Participants can interpret patterns differently.D．The different directions activated visual memory.4．What would be the best title for this passage?A．The Brain's StructureB．The Brain's Activated PatternsC．The Brain's Special SkillD．The Brain's OrientationB[2020·沈阳市高三教学质量监测(三)]Bikes were invented when people felt the need for stable, fast and efficient vehicles. The idea of making a bike started in the 1790s. It was inspired by a toy.In 1792, it started off as a two－wheeled part attached to a rigid wooden frame. People would use their feet to move the bike. However, it wasn't really what people were looking for with a lot of faults. It was a kind of transport highly demanding human energy, and the other problem was the poor stability. The front wheel could not turn so one had to get off the bike to turn it. Therefore，there was a need for it to be improved, but it was not the same person who created it that changed it.In 1820 the bike yet again had a new twist. Not only could the front wheel turn，but it was made more comfortable as a back supporter was secured. But one still had to move it by pushing it by feet on the ground. If one wanted to ride this bike, which was called a “hobby horse”at that time, he should know how to keep his balance. The other impressive thing that had changed was the speed，which increased up to 15 kilometers per hour.Ten years later, there came the bike popular even today. Thiswas invented by a blacksmith who used the idea of a pivot(枢轴) to develop the bike. It did not stop there. People were never satisfied with it because times also did change. As other things were being improved, so were the bikes.Now with everything in place, there is a need to improve on the speed of these bikes. And the idea of it being only human-powered is out of date. Today bikes have been improved and remodeled but the resemblance to the original bikes is still there.5．What was one of the problems with the first bicycle?A．It was regarded as a toy.B．It had too many wheels.C．It had to be operated with efforts.D．It was too stable to turn the wheel.6．What can we know about the bike from the text?A．The bike popular with us today appeared in about1830.B．The bike was invented and improved by the same person.C．The bike made in 1820 had to be moved forward by hand.D．The bike was called a “hobby horse” when it first appeared.7．What remains similar in modern bikes compared with those in history?A．The structure. B．The speed.C．The safety. D．The weight.8．Which of the following can be the best title for the text?A．The Development of BikesB．The Invention of BikesC．The Impressions on BikesD．The Problems with BikesⅡ.完形填空In July, I went to New York on business. I had a lot on my plate and was under great stress. I just wanted to __1__ and breathe in some fresh air. Suddenly something __2__ my mind. I'd always longed to __3__ on the Greek island of Santorini, admiring its white buildings, and the blue water surrounding it. Thus the idea of taking a two－week European trip __4__ was born. It was something I had __5__ thought I'd be planning this soon in my life. I had always thought, if it did ever happen, it would be when I was __6__ and old,free from the workload.I would lie if I said I wasn't __7__. I'd driven alone across the US before, but traveling to other countries whose __8__ weren't the same as mine terrified me. I was worried that I wouldn't be able to communicate with anyone. __9__ it dawned on me that I had to __10__ my comfort zone if I wanted to follow my dreams. And if I let __11__ get in the way, I'd never get anywhere.__12__ I searched for other places to visit on my trip, I found Mykonos, Greece, which I liked just as much as I liked Santorini. When I arrived, it was like I was inside a dream. I couldn't __13__ what I was seeing and experiencing. The best part was the bus ride to Little Venice. Riding on the bus and staring at every __14__ thing I saw, I couldn't help feeling I had __15__ another dimension of life. I was having the time of my life.1．A.carry on B．get awayC．stay in D．go back2．A.changed B．slippedC．crossed D．shocked3．A.settle B．wanderC．serve D．hide4．A.alone B．cautiouslyC．aimlessly D．again5．A.never B．alreadyC．once D．often6．A.clumsy B．lonelyC．bored D．retired7．A.excited B．scaredC．disappointed D．puzzled8．A.cultures B．valuesC．customs D．languages9．A.Or B．ThusC．But D．So10．A.establish B．findC．step out of D．fall back to11．A.fear B．moneyC．danger D．communication12．A.Since B．UntilC．Before D．As 13．A.tolerate B．believe C．ignore D．explain 14．A.rare B．traditional C．familiar D．new 15．A.fled B．discovered C．foreseen D．created。
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课时作业(十九)
解:如图,过点 B 作直线 BE∥CD.因为 CD∥AF,所以 BE∥CD∥AF,所 以∠ABE=∠A=105°, 所以∠CBE=∠ABC-∠ABE=30°. 又因为 BE∥CD, 所以∠CBE+∠C=180°, 所以∠C=150°.
课时作业(十九)
素养提升
[探究题] 有一天,许威同学用“几何画板”画图,他先画了两条平行线
课时作业(十九)
6.如图,小明从 A 处出发沿北偏东 60°方向行走至 B 处,又沿北偏西 20°方向行走至 C 处,则∠ABC 的度数是 ( C )
A.80° B.90° C.100° D.95°
课时作业(十九)
[解析] C 因为向北方向线是平行的,所以∠A+∠ABF=180°,所以∠ ABF=180°-60°=120°,所以∠ABC=∠ABF-∠CBF=120°-20°=100°.
课时作业(十九)
解： (1)图①中,∠BED=∠B+∠D;图②中,∠BED=360°-∠B-∠D;图③中, ∠BED=∠D-∠B;图④中,∠BED=∠B-∠D. (2)(答案不唯一)选图①中的∠BED=∠B+∠D.
说明理由如下:
A.∠1=∠2 C.∠1+∠3=180°
B.∠3=∠4 D.∠3+∠4=180°
课时作业(十九)
[解析] D 如图,因为 AB∥CD,所以∠3+∠5=180°.又因为∠5=∠4,所以∠3+∠ 4=180°.故选 D.
课时作业(十九)
4.如图,AB∥CD,DE⊥CE,∠1=34°,则∠DCE 的度数为 ( D )
的角共有 7 个.
课时作业(十九)
三、解答题
13.如图,点 D 在射线 AE 上,AB∥CD,∠CDE=140°.求∠A 的度数.
解:因为∠CDE=140°, 所以∠CDA=180°-140°=40°. 因为 AB∥CD,所以∠A=∠CDA=40°.
课时作业(十九) 14.如图,AB∥DC,AD∥BC,问:∠A 与∠C,∠B 与∠D 的大小有何关系?为
(B )
A.40° B.50° C.100° D.130°
课时作业(十九) 2.如图,直线 a,b 被直线 c 所截,若直线 a∥b,∠1=108°,则∠2 的
度数为 ( C )
A.108° B.82° C.72° D.62°
课时作业(十九)
3.[2018·滨州] 如图,直线 AB∥CD,则下列结论正确的是 链 接 听 课例 2 归纳总结( D )
本课件仅供交流学习使用，严禁用于任何商业用途
全品学练考
数学
七年级 下册
新课标（BS）
第二章 相交线与平行线
课时作业(十九)
第二章 相交线与平行线
课时作业(十九)
[第二章 3 第1课时 平行线的性质]
课堂达标 素养提升
课时作业(十九)
课堂达标
一、选择题
1. 如 图 ,a ∥ b,c 与 a,b 都 相 交,∠ 1=50°, 则 ∠2 的 度数 是
A.34°
B.54°
C.66°
D.56°
课时作业(十九)
5.[2018·绵阳] 如图,将一块含有 30°角的三角尺的两个顶点放在直 尺的对边上.如果∠2=44°,那么∠1 的度数是 ( C )
A.14°
B.15° C.16°
D.17°
[解析] C 如图,因为∠ABC=60°,∠2=44°,所以∠EBC=16°. 因为 BE∥CD,所以∠1=∠EBC=16°.故选 C.
课时作业(十九)
10.如图所示,已知 AB∥CD,BE 平分∠ABC,交 CD 于点 D.若∠CDE=150°,
则∠C 的度数为 120° .
课时作业(十九)
11.如图,直线 l1∥l2,∠α=∠β,∠1=40°,则∠2= 140 °.
课时作业(十九)
12.如图,已知 AD∥EF∥BC,BD∥GF,且 DB 平分∠ADC,则图中与∠1 相等
AB,CD,然后在平行线间画了一点 E,连接 BE,DE 后(如图①),他用鼠标左 键点住点 E,拖动后,分别得到如图②、图③、图④等图形,这时他突然 一想,∠B,∠D 与∠BED 之间的度数有没有某种联系呢?接着许威同学通
过利用“几何画板”的“度量角度”和“计算”功能,找到了这三个角
之间的关系.
(1)你能探讨出图①至图④各图中的∠B,∠D 与∠BED 之间的关系吗? (2)请从所得的四个关系中选一个,说明它成立的理由.
D= 60 °.
[解析] 因为 DA⊥CE,所以∠DAE=90°.因为∠1=30°,所以∠BAD=60°. 又因为 AB∥CD,所以∠D=∠BAD=60°.故答案为 60.
课时作业(十九)
9.如图 K-19-9 所示,点 A 在直线 a 上,射线 AB,AC 分别交直线 b 于点 B,C. 若 a∥b,∠1=70°,∠2=40°,则∠3 的度数为 70° .
课时作业(十九)
二、填空题
7.如图,点 D,E,F 分别在 BC,AC,AB 上,如果 DE∥AB,那么∠A
+
∠AED =180° 或 ∠ B+
∠BDE =180°, 根 据
是 两直线平行,同旁内角互补 ;
如果∠CED=∠FDE,那么 DF ∥ AC ,根据是 内错角相等,两直线平行.
课时作业(十九) 8.[2018 · 湘 西 州 ] 如 图 ,DA ⊥ CE 于 点 A,CD ∥ AB, ∠ 1=30°, 则 ∠
解:如图,因为直线 AB∥CD,所以∠3=∠1=54°,∠2=∠5.因为 BC 平 分 ∠ ABD, 所 以 ∠ 4= ∠ 3=54°, 所 以 ∠ 2= ∠ 5=180°-54°-54°=72°.
课时作业(十九)
16.如图,一条铁路修到一个村子边时,需拐弯绕道而过,如果第一次拐 的角∠A 是 105°,第二次拐的角∠B 是 135°,第三次拐的角是∠C,这 时的道路恰好和第一次拐弯之前的道路平行,那么∠C 应为多少度?
什么?
解:∠A=∠C,∠B=∠D.理由如下: 因为 AD∥BC,所以∠A+∠B=180°. 因为 AB∥DC,所以∠C+∠B=180°, 所以∠A=∠C.同理可知∠B=∠D.
课时作业(十九)
15.[2018·重庆] 如图,直线 AB∥CD,BC 平分∠ABD,∠1=54°.求∠2 的 度数.
课时作业(十九)