三校生数学题（1）已知向量AB=（6,1）,向量BC=（x,y),向量CD=（-2,-3）,当向量BC∥DA时,求实数X

应该是已知向量AB=(5,3),点A(3,1),则点B的坐标为?
B（x,y）
x-3=5 x=8
y-1=3 y=4
所以点B(8,4)

agree vi.同意;持相同意见I cannot agree with you on this point.在这一点上,我不能同意你的意见.
sb agree with sb 同意某人的话,意见
sth agree with sb 某物,某事适应某人 agree to sb 建议 agree on sth 在某一点上取得一致意见
agree up sth 在某一点上取得一致意见 agree to do sth 同意干某事
break vt.打破;损坏;破坏 We should all take a little break before dessert. 吃甜点之前我们大家应该稍微休息一下. break down 机器坏了=go wrong 身体垮了/终止谈话 11) I had never seen a grown man break down and cry. 我从未曾看到过一个这么强壮的汉子痛哭失声.
break in 闯入,插话 break off 忽然停止讲话/断绝,结束/暂停工作,休息
break out (战争等)爆发;逃出(无被动式) break through 打破包围
break up 驱散,学校的放学 The police had to employ force to break up the crowd.警察不得不使用武力驱散人群. break away from 脱离,逃说,与...断绝来往/改变某种习惯
bring vt.拿来;带来;取来 I'll bring some of my pictures into the gallery. 我就带一些我的摄影到艺廊来. bring about =cause, result in, lead to bring down 使倒下,使下降 bring force 使产生,引起
bring forward 提出建议=put forward/提前
bring in =get in the pops/使得到某种收入 Mr. Li: Oh… would you kindly allow me to bring in h… would you kindly allow me to bring in the civet durian? It is the favorite of my sister.李先生：喔…您能允许我带些榴莲吗?它是我姐姐最喜欢的水果. bring back to one's mind 使回想起
bring up sb 抚养某人 bring up sth 提出 bring up 呕吐 bring to an end 结束=come to an end
call vt.叫喊;打电话给… I'll call the roll before class. 课前我要点名.
call on sb 拜访,号召 call at 访问(某人的家);(火车、船)停*
call for 需要 And there's a phone call for you, Mr. Bennett. Bennett先生 有你的电话.
call for sb 去接某人一起去做某事 call off 取消(计划,比赛)
call out (call out+to sb.)大声地叫 call up sb 打电话
call in 请进来 We'll call in a couple of days. 我们两三天后打电话.
carry vt.携带;运载;传送 Another generation to carry on the Stewart name. 这是承继Stewart家族香火的新一代.
carry out 进行到底,贯彻执行 4) Tomorrow, Sandra will carry out the garbage. 明天珊多拉将会收拾垃圾的. carry out 是成就、完成的惯用语,但在此地,一看便知并非这种意思.可把它想象做从厨房把 garbage 运到外面去.
carry on 进行下去,坚持下去 Another generation to carry on the Stewart name. 这是承继Stewart家族香火的新一代. carry away 拿走,入迷,被...吸引 carry forward 推进,发扬(精神)
carry off 抢走,夺走/获得奖品 carry through 进行到底,完成计划 carry sb through 使...渡过难关
catch vt.捉;抓住 vi.接住 We didn't catch anything. 我们什么也没有钓著.
catch up 赶上 33. He shut himself away for a month to catch up on his academic work.他与世隔绝一个月,力图把功课赶上去.
catch on 勾住,绊倒 catch at 想抓住 A drowning man will catch at a straw. 溺水者见草也要抓;急何能择. be caught in the rain 被雨淋 catch up with 赶上某人,补上工作
clear a.清澈[晰]的 vt.清除 It is said it will clear up tonight. 天气预报说今晚雨就会停.
clear up (天气)转晴,澄清事实,整理收拾 It is said it will clear up tonight. 天气预报说今晚雨就会停.
clear away 清除掉,去掉,消散 clear off 消除(积雪)等障碍,把...拆掉,擦掉,清除
come vi.到来; 变得; 到达 May I come in? 我能进来吗?
come across 偶然发现,偶然遇到
come on 快点(口),开始,到来,举行,走吧,一起去 Oh, come on now. 噢 别这样了.
come at 向...扑过来,向...袭击 7. We may come at another time.我们可以另找个时间来.
come down 倒下,(温度,价格)下降,病倒 come forward 涌现,主动地响应要求做某事
come in 进来,上市 And have you had an engineer come in to do an inspection? 你们可有一个工程师来做过检查吗
come from 来自于 I come from Japan. 我来自日本. come out 出来,出发,结果 Did Mitchell Johnson's review come out yet? Mitchell Johnson的评论出来了没有 ?
come to 苏醒,总共,达到,得到谅解 When will he come to see you? 他什么时候来看你?
come up sb 走进 come up 种子生长发育,被提出 and I'll come up with something. 我会想出个办法的.
come to one's rescuers 帮助
come true 实现 I know, but it's still a dream come true. 我知道 但这终究是一个梦想实现了.
cut v.割,切,削减,切断 they cut patches 剪下布块
cut sth in half 把...砍成两半 cut away 切除 He cut away a dead branch.他砍掉一根枯干的树枝.
cut through 走近路,剌穿 cut down 砍倒,减少,压缩(开支)
cut off 切断(关系,来往）,中止(电话,思维) 3. He was cut off from his fellows.他和同伴失去联系.
cut out 删掉/改掉(恶习),停止 in a short cut 诀窍
do v.aux.助动词(无词意) What do you call this in English? 这个用英语怎么说?
do with 涉及到 What are you going to do with the books? 你打算拿这些书怎么办?
do up one's hair 盘起长发 do up sth 包/捆起来 do out 打扫,收拾
do away with =get rid of 废除,去掉,取消
die vi.死亡; 枯死; 熄灭 I will die before I'll eat that carrot. 如果要我吃胡萝卜,我宁愿去死.
dir from 因饥渴,战争,被污染的意外死亡 die off 因年老,疾病而死亡
die away 声音变弱,渐渐消失/停息,消失 die down 慢慢地熄灭(风,火)
die out 熄灭,变弱,消失,灭绝(动物)
fall vi.落下;跌倒;陷落 to fall 坠下,掉下
fall a sleep 去睡觉=go to sleep fall ill 病了 335. Be careful not to fall ill． 注意不要生病了.
fall across 遇见(偶然) fall back 后退,后撤 fall behind 落后,跟不上
fall in 集合/陷入 29. The necessary outcome of a war is a fall in production.战争带来的必然结果就是生产力下降.
fall into 陷入+名词 A fall into a pit, a gain in your wit.吃一堑,长一智.
fall off 减少,从...摔下来 to fall off a bench 从长椅上掉下来 fall on 看到,落在...上面
fall short of 缺乏 fall out of 放弃
get vi.变得,成为;到达 When do you get up everyday? 每天你几点起床?
get about 到处走,消息的传开 Don't forget about the bet. 别忘了打赌的事.
get across 穿过,讲清楚使人了解,领会The children began to get across at each other. 孩子们开始争吵了. get away 逃掉,离开,摆脱 1. I hope to get away early in the morning.我希望一早就动身离开.
get down 从…下来,写下来,记下来,病了/使某人不安 It's time to get down to business now. 是进入正题的时候啦.
get along with sth 进展得 get along with sb 相处
get in 进去,进站,收进来,收帐 Yeah. Yeah. Let's get in our lines. 是啊 是啊.请排好位置.
get off 离开,下车 You can take the bus and get off at the second stop. 你可以坐公共汽车第二站下.
get on 上车 157. Don't get on my nerves!（不要搅得我心烦.）

A
one-eyed是作定语修饰camel,所以冠词用A

这种考卷怎么可能在网上找到.当然要去书店买啦

第一志愿有15个选择,第二志愿就有14个选择,则有15*14=210种不同方法

新概念,李阳疯狂英语

An=1/8(an+2)²
当n=1时,a1=A1=1/8(a1+2)²
∴(a1)²-4a1+4=0
（a1-2)²=0
所以a1=2
a(n+1)=A(n+1)-An
=1/8[a(n+1)+2]²-1/8(an+2)²
∴8a(n+1)=[a(n+1)]²+4a(n+1)+4-[(an)²+4an+4]
那么[a(n+1)]^2-4a(n+1)+4=(an+2)^2
[a(n+1)-2]²-(an+2)²=0
[a(n+1)+an][a(n+1)-an-4]=0
∵an>0
∴a(n+1)-an-4=0
那么a(n+1)-an=4
即{an}为等差数列,公差d=4
∴an=a1+(n-1)d
=2+4(n-1)
=4n-2

设扇形半径为r,圆心角为Ф（弧度）,
则扇形面积S=Ф*r*r/2,
又r+r+Ф*r=20,解之得
r=20/（2+Ф）
代入面积公式自己化简就可以了.
顺便说一句,在百度打数学符号和数学公式实在太麻烦了.

求方程：z²+5+12i=0的解.
z²=-5-12i=13{cos[π+arctan(12/5)]+isin[π+arctan(12/5)]}
=(12/5)[-cosarctan(12/5)-isinarctan(12/5)]
故z=-[(2/5)√15]{cos[2kπ+arctan(12/5)]/2+isin[2kπ+arctan(12/5)]/2},(k=0,1)
即z₁=-[(2/5)√15]{cosarctan(12/5)+isinarctan(12/5)]=-[(2/5)√15][(5/13)+(12/13)i]
=-(2√15)/13-i(24√15)/65]
z₂=-[(2/5)√15]{cosarctan(12/5)-isinarctan(12/5)]=-[(2/5)√15][(5/13)-(12/13)i]
=-(2√15)/13+i(24√15)/65]

B.Given
被别人给了好机会 过去分词表被动吧

1 clear,是指清澈,清楚,这里指天变晴.
2 彩电,所以选a.b应该是指上了色的.c,是指多彩的,一般是指衣服啊,多种颜色.d,没颜色的.
3 d是指苏醒,恢复仪式.一,指来自.二,指遇见,碰见.三,加油.
4 complain是一类特别的单词,后面不能借双宾语,接某人加to
5 固定搭配.第四个答案,没见过.只看见过,think of sb as...
6 拾棍子防狗咬.所以是一种自卫行为,用第四个答案最合适.
强烈要求加分!日子咋就这么不好过呢?

由a8+a10+a13+a15=28得2（a11+a12）=28,及a11+a12=14
S22=（a1+a22）+(a2+a21)+...**a1+a22=a2+a21=...=a11+a12**
=11*(a11+a12)
=11*14
=154

基本公式向量AB+BC=AC
PQ-MQ+MP=（MP+PQ）-MQ=MQ-MQ=零向量

　　 高中英语作文常用句型
　　一、根据衔接词本身在文章中起到的作用,主要分为以下四类,即“起”、“承”、“转”、“合”.
　　(一)表示“起”的词/词组：用于开篇引出扩展句.
　　at first 最初 for one thing…(for another)
　　at present 现在;当今 首先…(其次)…
　　currently 目前;最后 recently　最近
　　first(ly)第一 in general 一般说来
　　in the beginning 起初 one the one hand…(on the other hand)
　　to begin with 首先;第一 一方面…(另一方面)
　　first of all 首先;第一 generally speaking 一般地说
　　in the first place 首先;第一 on the whole 总起来说
　　lately 最近 to start with 首先;第一
　　presently 现在;此刻 now 现在
　　(二)有关“承”的常用词语：用来承接上文.
　　after/after that/afterwards此后 by this time 此时
　　after a few days 几天以后 certainly 无疑地;当然地
　　after a while过了一会儿 therefore 因此;结果
　　also/too 并且;又 for example 例如
　　at the same time 同时 for instance 例如
　　beside 此外 for this purpose 为了这个目的
　　Besides/what,s more 而且;此外 from now on 从此
　　in addition 此外 second 第二;第二点
　　in addition to… 除…之外 secondly 第二
　　in fact 事实上 similarly 同样地
　　in other words 换句话说 so 所以
　　in particular 特别(地) soon 不久
　　in the same way 同样地 still 仍然
　　by the way 顺便提一句 then 然后
　　indeed 的确 third 第三;第三点
　　meanwhile 与此同时 thirdly 第三
　　moreover 而且,此外 for another 其次
　　no doubt 无疑地 such as 正如
　　obviously 明显地 later 后来
　　of course当然 truly 事实上;真实地
　　particularly特别地 unlike …不像……;和……不同
　　what is more 而且;此外
　　(三)有关“转”的常用词语：用来表示不同或相反的意见.
　　after all 毕竟 fortunately 幸运地
　　all the same 依然;照样 however 然而;无论如何
　　anyway 无论如何 in spite of 尽管……;虽然……
　　at the same time同时;然而 luckily 幸运地
　　but 但是 by this time 此时
　　though/although 尽管 no doubt 无疑地
　　in/by contrast 对比之下 on the contrary 相反地
　　even though即使 otherwise 否则
　　still 仍然 unfortunately 不幸地
　　in fact 事实上 unlike 不像……;和……不同
　　as a matter of fact 事实上 yet仍;然而;但是
　　especially 特别地
　　(四)有关“合”的常用词语：用于小结上文或结束本段落的内容.
　　above all 最重要的是 accordingly 于是
　　as a result结果 in sum 总之,简而言之
　　as has been noted 如前所述 in summary 简要地说
　　as I have said 如我所述 on the whole 总体来说;整个看来
　　at last 最后 therefore 因此
　　by and large 一般说来 thus 因此
　　briefly 简单扼要地 to speak frankly 坦白地说
　　by doing so 如此 to sum up 总而言之
　　eventually 最后 surely 无疑
　　finally 最后 to conclude 总而言之
　　in brief 简言之 no doubt 毫无疑问
　　in conclusion 总之,最后 undoubtedly 无疑
　　in short 简而言之 truly 的确
　　in a word 总之 so 所以
　　certainly 当然地;无疑地 obviously 显然
　　all in all 总之
　　二、根据衔接词本身的意思和文章连接所需要的逻辑意义,可分为以下14类.
　　(一)表示因果关系
　　as a result
　　He never studied hard, and as a result he failed in the last examination.
　　as a result of
　　He is late for work as a result of traffic accident.
　　accordingly
　　He wanted to buy a radio for study English, and accordingly her mother bought it for him.
　　because(of)
　　We are delayed because of a traffic jam.
　　due to
　　His success is due to his excellent work.
　　owing to
　　Owing to his absence, our meeting is not held.
　　thanks to
　　Thanks to a good teacher, she passed the examination.
　　now that
　　Now that you have grown up, you must earn for yourself.
　　so long as
　　You could realize your dream so long as you try it again and again.
　　since
　　Since you are here now, you,d better give a hand.
　　in that
　　The policy is harmful in that it may encourage people to give up.
　　so that
　　The office speaks at the top of his voice so that every soldier could hear him.
　　therefore
　　There is a calculating mistakes there, therefore, the answer is wrong.
　　(二)表示解释关系
　　as a matter of fact
　　I will go there this morning, as a matter of fact, I am only 10 minutes, drive from you.
　　as well
　　I will go there. My friend will go with me as well.
　　frankly speaking
　　Frankly speaking, I am not very satisfactory with your words.
　　in this case
　　In this case, I will go there as soon as possible.
　　(三)表示推理关系
　　or else
　　Hurry up, or else you,ll be late.
　　otherwise
　　You must carry this passport, otherwise you will be stopped by the guard.
　　if so
　　If so, it will make a great difference.
　　(四)表示递进关系
　　in addition
　　I need your help. In addition, I also need her support.
　　besides
　　First, we must work hard. Besides, we must work with a creative mind.
　　and moreover
　　The hat is the right size for you, and moreover, it goes well with your skin.
　　that is to say
　　The stock price is declining, that is to say, I am losing money.
　　in other words
　　I am not hungry, in other words, I really dislike the food in this canteen.
　　equally important
　　You should read more news from newspapers, and equally important, keep an eye on the news from the radio.
　　what,s more
　　It is harmful to my health, and what,s more, it is no good to my work.
　　last but not least
　　Last but bot least, my thanks should go to every member of my class.
　　(五)表示比较关系
　　equally
　　As a teacher, I should teach well, but equally, I should study well.
　　in the same way
　　It is such a coincidence that we figure it out in the same way.
　　in contrast to
　　In contrast to your belief, I quite disagree with you.
　　instead
　　If you don’t go, I,ll go instead.
　　on the contrary
　　You thought I like it. On the contrary, I dislike it.
　　in contrast
　　It is hot in the daytime, but in contrast it,s very cold at night.
　　while
　　We are happy in China, while most Africans live unhappily.
　　高中英语作文经典句型
　　一、~ the + ~ est +名词+(that)+主词+ have ever + seen(known/heard/had/read,etc)
　　~ the most +形容词+名词+(that)+主词+ have ever +
　　seen(known/heard/had/read,etc)
　　例句：
　　Helen is the most beautiful girl that I have ever seen. 海伦是我所看过最美丽的女孩.
　　Mr. Chang is the kindest teacher that I have ever had. 张老师是我曾经遇到最仁慈的教师.
　　二、Nothing is + ~~~ er than to + V Nothing is + more +形容词+ than to + V
　　例句：Nothing is more important than to receive education.　没有比接受教育更重要的事.
　　三、~~~ cannot emphasize the importance of ~~~ too much.(再怎么强调……的重要性也不为过.)
　　例句：We cannot emphasize the importance of protecting our eyes too much.
　　我们再怎么强调保护眼睛的重要性也不为过.
　　四、There is no denying that + S + V……(不可否认的……)
　　例句：There is no denying that the qualities of our living have gone from bad
　　to worse.
　　不可否认的,我们的生活品质已经每况愈下.
　　五、It is universally acknowledged that +句子~~(全世界都知道……)
　　例句：It is universally acknowledged that trees are indispensable to us.
　　全世界都知道树木对我们是不可或缺的.
　　六、There is no doubt that +句子~~(毫无疑问的……)
　　例句：There is no doubt that our educational system leaves something to be
　　desired.
　　毫无疑问的我们的教育制度令人不满意.
　　七、An advantage of ~~~ is that +句子(……的优点是……)
　　例句：An advantage of using the solar energy is that it won't
　　create(produce)any pollution.
　　使用太阳能的优点是它不会制造任何污染.
　　八、The reason why +句子~~~ is that +句子(……的原因是……)
　　例句：The reason why we have to grow trees is that they can provide us with
　　fresh air.
　　The reason why we have to grow trees is that they can supply fresh air for
　　us.
　　我们必须种树的原因是它们能供应我们新鲜的空气.
　　九、So +形容词+ be +主词+ that +句子(如此……以致于……)
　　例句：So precious is time that we can't afford to waste it.时间是如此珍贵,我们经不起浪费它.
　　十、Adj + as + Subject(主词)+ be,S + V~~~(虽然……)
　　例句：Rich as our country is, the qualities of our living are by no means
　　satisfactory. {by no means = in no way = on no account一点也不}
　　虽然他们的国家富有,他们的生活品质却不太令人满意.
　　十一、The + ~er + S + V,~~~ the + ~er + S + V ~~~
　　The + more + Adj + S + V,~~~ the + more + Adj + S + V ~~~(愈……愈……)
　　例句：The harder you work,the more progress you make.　　你愈努力,你愈进步.
　　The more books we read,the more learned we become.　我们书读愈多,我们愈有学问.
　　十二、By +Ving,~~ can ~~(借着……,……能够……
　　例句
　　By taking exercise,we can always stay healthy. 借着做运动,我们能够始终保持健康.
　　十三、~~~ enable + Object(受词)+ to + V(……使……能够……)
　　例句：Listening to music enable us to feel relaxed. 　　听音乐使我们能够感觉轻松.
　　十四、On no account can we + V ~~~(我们绝对不能……)
　　例句：On no account can we ignore the value of knowledge.
　　我们绝对不能忽略知识的价值.
　　十五、It is time + S +过去式(该是……的时候了)
　　例句：It is time the authorities concerned took proper steps to solve the
　　traffic problems.
　　该是有关当局采取适当的措施来解决交通问题的时候了.
　　十六、Those who ~~~(……的人……)
　　例句：
　　Those who violate traffic regulations should be punished.违反交通规定的人应该受处罚.
　　十七、There is no one but ~~~(没有人不……)
　　例句：There is no one but longs to go to college. 　　没有人不渴望上大学.
　　十八、be + forced/compelled/obliged + to + V(不得不……)
　　例句：Since the examination is around the corner,I am compelled to give up
　　doing sports.
　　既然考试迫在眉睫,我不得不放弃做运动.
　　十九、It is conceivable that +句子(可想而知的)
　　It is obvious that +句子(明显的)
　　It is apparent that +句子(显然的)
　　例句：It is conceivable that knowledge plays an important role in our life.
　　可想而知,知识在我们的一生中扮演一个重要的角色.
　　二十、That is the reason why ~~~(那就是……的原因)
　　例句：Summer is sultry. That is the reason why I don't like it.
　　夏天很燠热.那就是我不喜欢它的原因.
　　二十一、For the past +时间,S +现在完成式……(过去……年来,……一直……)
　　例句：For the past two years,I have been busy preparing for the examination.
　　过去两年来,我一直忙着准备考试.
　　二十二、Since + S +过去式,S +现在完成式.
　　例句：Since he went to senior high school,he has worked very hard.
　　自从他上高中,他一直很用功.
　　二十三、It pays to + V ~~~(……是值得的.)
　　例句：It pays to help others. 　　帮助别人是值得的.
　　二十四、be based on(以……为基础)
　　例句：The progress of thee society is based on harmony. 　社会的进步是以和谐为基础的.
　　二十五、Spare no effort to + V(不遗余力的)
　　例句：We should spare no effort to beautify our environment.
　　我们应该不遗余力的美化我们的环境.
　　二十六、bring home to +人+事(让……明白……事)
　　例句：We should bring home to people the value of working hard.
　　我们应该让人们明白努力的价值.
　　二十七、be closely related to ~~(与……息息相关)
　　例句：Taking exercise is closely related to health. 　　做运动与健康息息相关.
　　二十八、Get into the habit of + Ving = make it a rule to + V(养成……的习惯)
　　例句：We should get into the habit of keeping good hours.　　我们应该养成早睡早起的习惯.
　　二十九、Due to/Owing to/Thanks to + N/Ving,~~~(因为……)
　　例句：Thanks to his encouragement,I finally realized my dream.
　　因为他的鼓励,我终于实现我的梦想.
　　三十、What a + Adj + N + S + V!= How + Adj + a + N + V!(多么……!)
　　例句：What an important thing it is to keep our promise!
　　How important a thing it is to keep our promise!遵守诺言是多么重要的事!
　　三十一、Leave much to be desired(令人不满意)
　　例句：The condition of our traffic leaves much to be desired.　我们的交通状况令人不满意.
　　三十二、Have a great influence on ~~~(对……有很大的影响)
　　例句：Smoking has a great influence on our health. 抽烟对我们的健康有很大的影响.
　　三十三、do good to(对……有益),do harm to(对……有害)
　　例句：Reading does good to our mind. 读书对心灵有益.
　　Overwork does harm to health. 工作过度对健康有害.
　　三十四、Pose a great threat to ~~(对……造成一大威胁)
　　例句：Pollution poses a great threat to our existence.　污染对我们的生存造成一大威胁.
　　三十五、do one's utmost to + V = do one’s best(尽全力去……)
　　例句：We should do our utmost to achieve our goal in life.我们应尽全力去达成我们的人生目标

找老师给你补课,或者你自己静下心来把书认真的看过去,遇到不会的拿出来问!

提示：一元二次方程有复根时,两复根为共轭复根.
另一根为2-3i,由韦达定理得
(2+3i)+(2-3i)=-b/2
(2+3i)(2-3i)=c/2
b=-2[(2+3i)+(2-3i)]=-8
c=2(2+3i)(2-3i)=2×(4+9)=26
b=-8 c=26

第一题：above all： 副词用法,表最重要,在其他因素之上地.
而in all:总共(意思不对)；as well:和,也（与and重复）；at least:至少（语气不对,没这么层层递进法的）
第二题：absent from：缺席（状态）.
而absent in没这种用法；away with：把...拿走[带走],离开（他是根本没来,不是离开）；short of ：缺乏（就是少什么的意思,跟这题表达的意思没关系）----建议这题直接背答案,当初都是这么过来的,不要用中文思维,就是这么用的.
PS.应该对的:)

（1）f(2)=loga2=-1=log1/22,
a=1/2.
∴f(x)=log1/2X.
（2)∵log1/2m≥-1=log1/22,
又y=log1/2X是减函数,
∴0

我是13年三校的,高考语文背诵古诗文是伐檀,梦游天姥吟留别,登高,山坡羊潼关怀古,琵琶行第二段,雨霖铃,秋思,劝学,学记第二段,师说,伶官传序第一 四段,陈情表第一段.没写段落的就是全文背诵.14年如果不增加就还是这些,
一楼回答的应该是高中的,三校没有那么难.

1.画个图 夹角是60°对吧,然后两条边分别是50和40,也就是在这种情况下求三角形的另一条边 余弦定理就行了
2.-f(x)=f(x+pai),那么f(x)=f(x+2pai),说明周期是2.f(-x)=f(x)说明是偶函数 所以f(x)= cosx
3.（1）把分母里的1变成sin的平方+cos的平方 sin2a和cos2a 也化简 然后分子分母提公因式 约分 行了
（2）不好意思题目看不懂
4.设AB是4X AC是3X 用余弦定理求出BC（含x）再用正弦定理就可以求出sinC
5.设三边分别是 a b c 然后a+b+c=20 1/2乘以bcsin60°=为10倍根号 再根据余弦定理列一个方程 三个方程就能解出来
6.设三角形ABC中,∠A大于B大于C 则相对应的边就是a>b>c A=2C 全不用c表示出来那么a=c+2 b=c+1 再用正弦定理列方程
7.题目没有问题吗?
8.角a的终边是3x-4y=0(x>=0 画个图 则sina=3/5 cosa=4/5 后面没问题了吧

第一题：must have done表示一定做了某事,而should have done表示本应做某事（实际没做）,句意表示他一定是完成了他的工作,否则他在海边不会玩的那么开心.
第二题：A时态就有错误,后面是had,而A是runs,C表示伴随,可理解为由于、因为
第三题：祈使句,此举表示鼓励,应用祈使句.
第四题：as 是从属连词,说明一般的因果关系,它引导的从句通常放在句首,有时也可放句末.for 是并列连词,用来附带解释说明前一分句的原因或理由,for引导的并列句,一般放在所要说明的句子的后面.
第五题：从句意上理解,所有的邻居都钦佩这个家庭,在这父母对待孩子像朋友一样.可以理解成一个虚的地点.
第六题：nothing to gain一无所获.A表示挣得,B表示追赶,D表示抓住,掌握,C表示获得
第七题：look into调查,A、B表示寻找,C表示进入、加入.句意表示我许诺调查这件事情
第八题：rise 是不及物动词,没有被动语态.raise 是及物动词,在此题中表示提高,抬高.

欧米伽ωX+φ为相位,X=0时的φ为初相

(cosa)²=1-（sina）²=9/25
a在四象限cosa>0
所以cosa=3/5
tana=sina/cosa=-4/3