1.若关於x的一元2次方程x^2sin(a)+2x(sin(a)+2)+sina+12=0有实数根,试确定锐角a的范围

PR是圆的直径,PR所对的角等于直径所对的角等于90度,连接PR中点与Q、S,则可得直角三角形斜边的中线等于斜边的一半

Some books are to be tasted, others to be swallowed, and some few to be chewed and digested; that is, some books are to be read only in parts; others to be read, but not curiously; and some few to be read wholly, and with diligence and attention.
Some books also may be read by deputy, and extracts made of them by others; but that would be only in the less important arguments, and the meaner sort of books; else distilled books are, like common distilled waters, flashy things.
Reading maketh a full man; conference a ready man; and writing an exact man. And therefore, if a man write little, he had need have a great memory; if he confer little, he had need have a present wit; and if he read little, he had need have much cunning, to seem to know that he doth not.
Francis Bacon Of Studies
那一整篇都是……

1.高原山地气候发生在海拔2000米以上的高原山地.
2.高原山地气候形成的原因是气温、水分条件会随着海拔的升高,出现明显的垂直变化与分布.海拔越高,气温越低,温差变化越小,湿度越大,高到一定的高度水分减少太多,湿度又会逐步下降.
3.高原山地气候的动植物或景观,在山地是“一山有四季,十里不同天”.在高原出现高寒地区的气候特征与动植物景观.

英音 a发梅花ai的音
美音 a发拼音中e的音

A Christmas wish for my best friend!
给我最好的朋友一个圣诞祝福!
A Christmas greeting to cheer you,my good friend.
献上令你开心的圣诞祝福,我的好友.
Why don't we enjoy our holidays together?
何不与我一起共度佳节呢?
We will beshavingsChristmas at David's this year.You are welcome to join us!
今年我们要在戴维家过圣诞,欢迎你来加入!
Take your passion and make it come true.
发挥你的热情,让美梦成真.
I hope we can spend the holidays together.
希望我们能一起过圣诞节.
I hope this card reaches you in time for Christmas.
希望你能在圣诞节前收到这张卡片.
Wishing you and your family all our blessings for a beautiful Christmas season!
给长辈
For you and your family,boss,during this holiday season!
值此圣诞佳节,老板,献给您及您的家人.
there's no place like home for the holidays.
在这佳节里,没有比家更好的地方了.
Best wishes for a wonderful new year.
献上最诚挚的祝福,祝您新年恰愉快.
May the joy of Christmas be with you throughout the year.
愿圣诞佳节的喜悦,伴随您在度过新的一年.
May joy and health be with you always.
祝您永远健康快乐.
May happiness follow you wherever you go!
愿您幸福快乐,直到永远永远.
A special card from your grandson.
您的孙子,寄上一张特别的卡片.
A Christmas wish from your nephew.
您的侄儿祝您圣诞快乐.
Wishing you and yours a happy happy new year.
万事如意,合家平安.
Your entire staff wishes you and yours a most happy Christmas.
全体职员祝您及家人圣诞快乐.

ax^2+2ax-(a+1)

科学.
因为人类目前对宇宙的认识是以科学观测事实、数学定律、物理定律、化学定律为基础的,以实证为原则,有严密的逻辑体系.
比如,作为现代宇宙学根基的广义相对论虽然看上去玄妙不可理解,但的确是以其推论被验证（利用日全食实测光线在引力场中的弯曲）为实证基础的.

s=-2,t=2

1.F=（G运动员+2*G滑雪板）/（2S滑雪板）=（76*10+2*12）/（2*2*0.1）2.F浮=ρ水*g*V排,其中V排=10立方分米3.静止时浮力等于重力,即为5牛4.(1)由F浮=ρ水*g*V球 可得到V球=F浮/（ρ水*g）(2)由G球=ρ球*g*V球可得到...

渐入佳境

not exclusively 意思是不全是.你理解得不错.

我说简单一点吧：
（1）因为DE是三角形ABC的中位线,所以DE:BC=1：2
梯形的中们线长为上底加下底和的一半,所以设DE=x,那么BC=2x
所以FG=3x/2 DE:FG:BC=1：3/2：2=2：3：4
（2）设AD=y,那么BD=3y,AB=AD+BD=4y AD/AB=y/4y=1/4

看来楼主对惯性理解的不对,惯性是物体的属性,决定它的大小是物理量是物体的质量,特别需要注意的是：一个力是不能与惯性平衡的,因为惯性不是力.
第二：因为太空船的质量不会消失,所以太空船的惯性也不会消失,并且惯性不会受其它因素的影响.也就是说,向心力不会影响惯性的大小（注意：惯性是性质,它没有方向）.
对楼主的问题的标准解释方法是（用初中的惯性方面的知识来解释,如果用高中的力和曲线运动的知识解释起来是特别简单的）：太空船关闭引擎后,它有沿着引擎关闭前一瞬间的那个速度方向直线飞离地球的趋势,但是地球对它的引力（这里充当了向心力）又使它有向下落的趋势,这两个趋势的综合就决定了它沿圆轨道（或椭圆轨道）绕地球运行.
同样的,地球等行星绕太阳运行、太阳与其它无数恒星绕银河系中心运行都是相同的原因.
（做为物理教师,希望我的回答能够帮助楼主理解这方面的知识）

(1)
x=1 y=-2,x=3 y=8,x=-1,y=-4分别代入方程,得到关于a,b,c的三元一次方程组.
a+b+c=-2 (1)
9a+3b+c=8 (2)
a-b+c=-4 (3)
(1)-(3),得b=1
[(1)+(3)]/2,得a+c=-3 c=-3-a,代入(2)
9a+3-3-a=8 8a=8 a=1 c=-3-a=-4
a=1 b=1 c=-4
(2)
平方项和绝对值项均恒非负,现在互为相反数,则均=0
2a+b=0 b=-2a
2b+c=0 c=-2b=4a
3a+2b-c=0
3a-4a-4a=0 5a=0
a=0 b=0 c=0
(3)
(2x-y)(x-2y)=5
将5分解质因数：
5=1*5=(-1)(-5)
得到关于x,y的4个方程组：
2x-y=1 x-2y=5 解得x=-1 y=-3
2x-y=5 x-2y=1 解得x=3 y=1
2x-y=-1 x-2y=-5 解得x=1 y=3
2x-y=-5 x-2y=-1 解得x=-3 y=-1
方程的整数解为：
x=-1 y=-3或x=3,y=1或x=1,y=3或x=-3,y=-1

如图,已知长方形的周长=2r+2πr=16.53分米
π取3.14,得 2r+6.28r=16.53 分米
8.28r=16.53分米
r=2 分米
圆面积=πr²=3.14×2²=12.56平方分米

乙酰胆碱受体包括两种：毒蕈碱型受体（M受体）,产生副交感神经兴奋效应,既心脏活动抑制,支气管胃肠平滑肌和膀胱逼尿肌收缩,消化腺分泌增加,瞳孔缩小等.阿托品为毒蕈碱受体阻断剂.烟碱型受体（N受体）,N1位于神经节突触后膜,可引起自主神经节的节后神经元兴奋,N2受体位于骨骼肌终板膜,可引起运动终板电位,导致骨骼肌兴奋.六烃季胺主要阻断N1受体功能,筒箭毒碱阻断N2受体功能.
在接受交感神经节后纤维支配的各种器官中存在着与肾上腺素、去甲肾上腺素起反应的受体,称为肾上腺素能受体.其化学性质尚不清楚.用对药物反应的方法,肾上腺素能受体可分为α及β两个类型.肾上腺素对α及β两型受体均起作用,而去甲肾上腺素主要对α型起作用.α型受体所引起的反应为血管收缩、瞳孔扩散等,α受体可被dibenamine、麦角毒等α阻断药所抑制.β受体所引起的反应为支气管扩张、血管扩张等,β受体可被3,4－dichloroisoproterenol（D－CI）等阻断药物所抑制.
肾上腺素能受体可分为α和β两类.α受体的阻断剂是酚妥拉明,β受体的阻断剂为心得安.
拮抗剂与激动剂相对,与受体结合后,但不能诱导产生生物活性变化的构象变化.而激动剂是能够诱导受体构象变化而引起生物活性.
拮抗剂是指与受体只有较强的亲和力,而无内在活性的药物,故不产生效应,但能阻断激动药与受体结合,因而对抗或取消激动药的作用.
阻滞剂（beta blockers）
阻滞剂,目前有9种,如心得安、心得宁、心得平等.这类药物具有镇静的作用,使用范围主要在技能类难和准确性顶群中,目的是为了减少心脏的过度兴奋,降低焦虑稳定情绪.

其实你自己就已给出答案了.
氧自由基、过氧自由基的氧化性都很强.

答案错了 ,要么就是集合B那的=改掉
有绝对值就将不等号两边同时平方

1.一种食品罐头的包装：直径10㎝,高8㎝.
（1）在罐头盒的侧面贴一圈商标纸,所贴的商标纸的面积是多少平方釐米?
3.14×10×8=251.2平方厘米
（2）做这样的一个罐头盒,大约需要铁皮多少平方釐米、（接头处忽略不计）
3.14×10/2×10/2×2+3.14×10×8
=157+251.2
=408.2平方厘米
2.一辆压路机的滚筒是圆柱体,长2米,底面直径为1.5米,以每小时6千米的速度前进,这辆压路机每小时可以压路多少平方米?
6千米=6000米
3.14×1.5×2×6000
=3.14×18000
=56520平方米
3.会议大厅裏有10根底面周长为3.14米、高6米的圆柱形柱子.现在要刷上油漆,每平方米用油漆0.5千克,刷这些柱子一共要用油漆多少千克?
0.5×（3.14×6）×10
=0.5×188.4
=94.2千克
4.一个木制的直圆柱,它的底面半径是6釐米,高是15釐米,若沿著底面直径且垂直於底面把它切成相同的两个部分,每个部分的表面积是多少?
3.14×6×6+3.14×6×15+6×2×15
=3.14×36+3.14×90+180
=575.64平方米

http://zhidao.baidu.com/topic?ct=29&tn=iktopic&word=%bb%c6%ba%d3+%d1%e8%d3%ef

设1为方程x²-5x+m=0的根
则方程x²-5x+m=0的两根分别为：1、4
方程x²-10x+n=0的两根可为：2、8
此时1：2=4：8
m=4,n=16
m:n=1:4

word是单词,sentence是句子
翻译成中文：
1.我今天学了一个新单词
2.我今天学了一个新句子
手打的哦!希望楼主采纳啊

f(-x)=f(-x-1+1)=f(-(x+1)+1)=-f(x+1+1)=-f(x+2)

I have never seen such a man as he is.
I have never seen such men as they are.
变复数的话句意当然会变,变成了我从来没遇到过像他们这样的男人.
as 后面跟的名词不限定单数.such as中间不可数名词可以加.
（就是不明白你那个“片语”是什么意思啊?）
都可以.
Eg:1.Two of my books are the same as Lily's.
2.Some of my advice is the same as John's.
3.It's the same piece of advice that I put forward yesterday.
4.They are the same group of stranges that I met yesterday.
不知道你明白否,话说你这种问法闻所未闻,很是郁闷.

d) 适合复杂逻辑的自动设计与证明

楼上的UU过客,级别那么高,翻的什么东西啊,往来译成to and from,说明基本功不扎实
我在深圳,陪老外去香港的时候,问过出入境管理科的英语专业人员,答案是没有固定说法,证件上没有,政府官方网站上也没有,后来看凤凰卫视英语新闻的时候,碰巧听到了他们的说法：
Special Pass to the Mainland for Hong Kong and Macao residents

x1+x2=-2k x1x2=3
又x1²+x2²=10
∴(x1+x2)²-2x1x2=10
即：4k²-6=10
解得：|k|=1

怀着一颗感恩的心,去面对生活,去看待生活中的种种,只要心怀感谢,人生就会过得幸福而充实.
一个青年丢掉了工作,身在异乡的他四处寄求职信,但都石沉大海.一天,他收到了一封回信,回信人斥责他没有弄清楚该公司所经营的项目就胡乱投递求职信,并指出求职信中语句不通顺,借此把青年好好地嘲笑了一番.青年虽然有些沮丧,但他觉得这是别人给他回的第一封信,证实了他的存在,而且回信人在信中的确指出了他的不足.为此,他还是心怀感恩地回了一封信,里面对自己的冒失表示了歉意,并对对方的回复和指导表示了感谢.几个星期后,青年得到了一份合适的工作,录用他的正是当初回信拒绝他的公司.
这是我身边发生的一个真实故事,我一直以该青年为榜样,正是他那颗感恩的心,打动了用人单位.
常怀一颗感恩的心,这个世界在我们眼中就会变得愈加美好.
同样的一枝玫瑰,有人说：“花下有刺,真讨厌!”有人说：“刺上有花,真好!”看到刺的人,挑着毛病、盯着不足,他们注定是不快乐的.而那看到花的人,则有着感恩的心,尽管刺扎手,但那些刺上却有着芬芳的花朵,于是他能感受到幸福.所以,拥有感恩心的人是幸福的.
我们常说,生活中不是缺少美,而是缺少发现美.发现美,不光需要一双敏锐的眼睛,更重要的是要有一颗充满爱的心.我想说,感谢爱你的人吧,正是他们的关心、鼓励和支持才让你感到了生活的温暖和充实；感谢讨厌甚至恨你的人吧,是他们让你的生活曲折多彩,让你面对挫折时变得更坚强.这种爱就是一种感恩,爱世间万物,感激世间万物,用一颗感恩的心去“打量”万物,那上面定有细微之处让你心怀感恩.
感恩———幸福的真谛!

树不会自己栽,而是被栽,所以要用被动语态be done
must后跟动词原形不跟to do
有can be donemay be done的形式
例如The test can be/may be delayed

1)原不等式可化为（a-2)x2时,x0时,x0时,x

最大位移0.04m
所以最大回复力为F=kx=50*0.04=2N
最大加速度a=F/m=2/（12.5*10(-3)）=160m/s^2

质量越大的物体不是受的重力越大越快掉下来吗?
这个问题为自由落体运动,16世纪末,伽利略通过反复的实验,认为如果不计空气阻力,轻重物体的自由下落速度是相同的.
至于老师说的F=am,其实你可以把F=mg代进去,就可以看出来了,a=g,
自由落体与质量大小并无关系.
回到你提的两个人掉到一样的距离,由于自由落体与质量大小并无关系,两个人飞出来的初速度一样,落地时间相同,那么他们也就自然掉一样远了.

影响电阻的原因有温度和使用的电阻的材料,不同的材质的电阻不同,铜的比铁的电阻小,比金子和银子的大,温度越高电阻越大

Achievements
Michael Jackson has set many records throughout his career and won many awards.From the early days of the Jackson 5 to the current day.Michael Jackson has been in a league of his own with his best competition being himself and trying to improve on what he has already achieved.
He are a just a few of the record breaking achievements.
Biggest Selling Album Of All Time - Guiness Book Of World Records
Michael Jackson's "Thriller" Album is the biggest selling album of all time,with over 50 million copies sold worldwide.Thriller is also the biggest selling U.S album with sales of 25 million copies.
Most No1 Hits in 1980's
By The End of the 1980's MIchael Jackson had more #1 hits than any other artist for the decade.
Greatest Audience - Guiness Book Of World Records
The highest-ever viewership was 133.4 million viewers watching the NBC transmission of Super Bowl XXVII on June 31,1993.Michael was spotlighted during the half-time peformance.
Bad Tour - Guiness Book Of World Records
Michael Jackson's world tour brought in a record gross revenue of over $124 million during September 1987-December 1988.
100 Million Records
Michael has sold over 100 million singles and albums outside of the U.S.
Billboard Charts
Michael Jackson is the first person in the 37 year history of the Billboard chart to enter straight in at No1,with his single "You Are Not Alone".The previous record "Earth Song" which had debuted at No5 and also Michael Jacksons.
Biggest Selling Video
Michael Jackson's "The Making Of Thriller" is the biggest selling video to be released by an artist.
Billboard "Hot 100" Singles Chart
Most No1 Hits by Male Artist (13)
No1 Debuts
Michael Jacksons "Bad","Dangerous",and "HIStory" albums all debuted in at No1.
Awards
Michael has won more awards than any other artist.
No1 On Charts
In 1983 Michael became the first artist to simultaneously hold the number one spots on Billboard's rock albums and rock singles charts,as well as the R&B albums and singles charts.
Consecutive No1 Singles
Jackson 5 were the first group to ever have four consecutive No1 singles.

猪突豨勇
zhū tū xī yǒng
〖解释〗豨：野猪.指拼命向前冲,不怕死的人（含贬义）.
〖出处〗《汉书·食货志下》：“匈奴侵寇甚,莽大寡天下囚徒人奴,名曰猪突豨勇.”
【犬彘之食】 比喻食物非常粗糙.

如果不知道单位的本意,还真弄不明白现在这两个意思.
“单位”原指佛教禅林僧堂中僧人坐禅的座位.《敕修百丈清规——日用轨范》：“昏钟鸣,须先归单位坐禅.”后指计算事物数量的标准,又称某一工作部门为单位.
单位,在佛教中有两个意思.一为数量的数词,即用以测量长度、质量、时间等的定量.佛教中的数量单位比现实中的数量单位复杂得多,以时间为例,我们俗人说“刹那”是指瞬间、极短的时间.佛学就丰富多了,刹那是指一个心念起动的极短时间即为一“念”,20念为一瞬,20瞬为一弹指,20弹指为一罗预,20罗预为一须臾,30须臾为一昼夜,如此算来,一刹那就是0.018秒.刹那、一瞬、弹指、须臾等模糊不清的时间概念,在佛教中都有精确的数据,您说复杂不复杂.单位的另一意思是指禅林僧堂中,僧人坐禅的座床,因为在座床上贴有各人的名单且占一个位置,故称单位.（见《敕修百丈清规》卷下）

① 通分：
2mn／4m²－9 与 2m－3／2m－3 （“／”表示分数线）
2mn/(4m^2-9)=2mn/(2m+3)(2m-3) ,【分子不变,分母因式分解】
第二题好像应该是:(2m-3)/(2m+3)=(2m-3)^2/(2m+3)(2m-3) ,【分子分母同乘2m-3】
②应用题：
某村种植了m公顷玉米,总产量为n千克；水稻的种植面积比玉米的种植面积多p公顷,水稻的总产量比玉米总产量的2倍多q千克.写出表示玉米和水稻的单位面积产量（单位：千克／公顷）的式子.如果两式的分母不同,进行通分.
玉米的单位产量是:n/m
水稻的单位产量是:(2n+q)/(m+p)
通分:
n/m=n(m+p)/m(m+p),【分子分母同乘m+p】
(2n+q)/(m+p)=m(2n+q)/m(m+p)【分子分母同乘m】

可直接用He requests an interview with docto

通分.变成
a:b=6:16
a:c=6:3
a:b:c=6:16:3

圆柱体和长方体的体积都是底面积乘高,底面积相同,高则相同,所以圆柱的高也是9厘米.
圆锥的体积是圆柱的三分之一,所以圆锥的高是9*3=27厘米
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A:Can I book the ticket here?
B:Yes.where do you leave for?
A:shanghai
B:OK .what date it is
A:April 4th.
B:morning ,afternoon or evening
A:Moring please
B:Sure.You can get your ticket using VISA or we can give you through mail.
A:Thank you!

只许周官放火,不许百姓点烟.
责人以严,待己以宽.

My one breath reads off the fairy tale which "Sea Daughter" this Anderson writes to give me to be specially deep."Sea Daughter" this article everybody is certainly very familiar!"Sea Daughter" in the fairy tale leading character lives in the sea deep place,is a mermaid.She might pass for more than 300 years years in the seabed world,then changed into the froth,finished her life happiness.Her life is longer than several times the humanity,but she does not have the human unique that kind “not to extinguish the soul”.In order to obtain this inspiration she to give up in the sea life,she endures these pain from already the fish tail changed into a two person leg.Afterward she liked a prince,obtained a humanity's soul.That prince and the world female has married,her hope did not have.If she continues to become “the sea daughter”after must assassinate that prince,may return to her in the family member,returns to belongs to her from already world.But she does not have to do this actually from has thrown in entering the sea to change into the froth.I like "Sea Daughter".It caused me to understand the life was valuable.Must have the strong will in anticipation in any surface,goes bravely facing it.In this book,I have not only known some happy stories,but also receives the very big inspiration education.

1/5X+50=2/3X-6
2/3X-1/5X-50=6 -----等号两边同时加上2/3X,所以左边就是加号,右边的减去一个加上一个,正好为0.
(10/15-3/15)X-50=6 -----相对应 1*5+2*5=（1+2）*5一样的道理.
7/15X=56 -----等号两边同时加上50
X=56 /(7/15) -----等号两边同时除以以7/15,所以左边的X前面正好是1.(补充一下,这里你计算错了,应该是除以）
X=120
这样解释应该容易懂一些
至于你说去掉加号减号变加号,或者加号变减号.
举例来说吧
10-（5+2） = 10 -5 -2.
为什么这样呢?左边的意思是 10减去2个数的和.右边的意思是 10依次减去2个数.这两个的结果是一样的.所以括号里的+要变-.
同样道理,10-(5-2)=10-5+2.
如果括号前面是加号,去掉括号就不要变号了
如
10+(5+2)=10+5+2
左边的意思是 10加上2个数的和.右边的意思是 10依次加上2个数.这两个的结果是一样的.所以括号里的不变号.
10+(5-2)=10+5-2
这样是一样的.
记住就可以了

要求 x^2+3x+2>=0 且 3x>0
即 (x+1)(x+2)>0且 x>0
得到定义域为 (0,+无穷)

1 孔子说“性相近也，习相远也” “By nature ,near together,; by practice far apart.”
2孔子主张“有教无类” “There is a difference in instruction but none in kind.”
3 但他“削迹于卫，伐树于宋，穷于商周，围于陈蔡”，
4“学而优则仕” “The energy that he has left after studying , he should devote to service of State.”
5孔子说：“中人以上，可以语上也；中人以下，不可以语上也”，Th Master said,To men who have risen at all above the middling sort ,one may talk of things higher ye. But to men who are at all below the middling sort it is useless to talk of things that are above them.
6《论语》“先进”篇中记载
7“公冶长”篇中记载
8“不愤不启，不悱不发，举一隅不以三隅反，则不复也”，Only one who bursts with eagerness do I instruct; only one who bubbles with excitement, do I enlighten. If I hold up one corner and a man cannot come back to me with the other three, I do not continue the lesson.
9“知之者不如好之者，好之者不如乐之者”，” To prefer it is better than only to know it. To delight in it is better than merely to prefer it.
10孔子自述“吾十有五而志于学”The Master said, At fifteen I set my heart upon learning.， “学而不止，阖棺乃止“，
11“学而不思则罔，思而不学则殆”，”He who learns but does not think ,is lost. He who thinks but does not learn is in danger.
12“学而时习之”，To learn and at due time to repeat what one has learn”;“温故而知新”,””reanimating the Ole can gain knowledge of the New”
13“知之为知之，不知为不知” “When you know a thing, to recognize that you know it, and when you do not know a thing, to recognize that you do not know it.”
14“三人行必有我师”，”Even when walking in a party of no more than three I can always be certain of learning from those I am with.” “见贤思齐”，”In the presence of a good man, think all the time how you may learn to equal him.”
15学习不仅要举一反三，“同8中翻译”。还要“闻一知十”，” Hearing one part in ten, in order to understand the whole ten.”
16因材施教
能找到的就这么多。所有出自《论语》原文的翻译，我是参考外语教学与研究出版社出版的《The Analects》，Arthur Waley翻译。

人固有一死,或重于泰山,或轻于鸿毛.—— 司马迁
生,亦我所欲也；义,亦我所欲也；二者不可得兼,舍生而取义者也.—— 孟轲
英雄---就是这样一个人,他在决定性关头做了为人类社会的利益所需要做的事.—— 伏契克
为着追求光和热,人宁愿舍弃自己的生命.生命是可爱的.但寒冷的、寂寞的生,却不如轰轰烈烈的死.—— 巴金

sinC/sin90=1/n
所以c=arcsin（1/1.31）=49.8
当入射角的角度大于49.8就可以发生全反射现象.