热点试题

[ 考点 ] 高三数学考点:平面的法向量

  • 平面的法向量:

    如果表示向量的有向线段所在直线垂直于平面α,则称这个向量垂直于平面α,记作⊥α,如果⊥α,那么向量叫做平面α的法向量。
     

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  • 法向量的特点:

    1.法向量一定是非零向量;
    2.一个平面的所有法向量都互相平行;
    3.向量是平面的法向量,向量是与平面平行或在平面内,则有
    4.已知一平面内两条相交直线的方向向量,可求出该平面的一个法向量,一个平面的法向量不是唯一的,在应用时,可适当取平面的一个法向量.

    一般地,由直线、平面的位置关系以及直线的方向向量和平面的法向量,可归纳出如下结论

     
     
    求平面法向量的方法与步骤:
     
     
  • 2016-05-16 | 0

    [ 考点 ] 八年级历史考点:汉朝治理黄河

  • 汉朝两次治理黄河:
    第一次:西汉初期,黄河下游决口,十几个郡县遭受洪灾,汉武帝下令治理黄河,亲临治河工地,命随从的文官武将都去背柴草,堵塞决口。影响:经过这次治理,有八十多年,黄河下游没有发生过大水灾。
    第二次:西汉末年,黄河水患又严重起来,东汉明帝令水利专家王景主持修河。经过几次十万人一年的辛勤劳动,疏通黄河,修建了千余里的黄河大堤。影响:黄河下游几十个县,被淹的土地又变成了良田,而且在以后的八百多年里,黄河没有改道。
  • 两汉时期的水利特色:
    两汉水利事业发展迅速并且有着明显的特色,黄河流域以营建灌溉渠为主;江汉之间以修天然的陂池为主;东南以排水筑堤、变湿地为良田;西北则是利用雪水或者地下水,修筑特殊的水利工程坎儿井。
    两汉针对黄河泛滥,西汉武帝和东汉明帝都进行了大规模的黄河治理工程,取得良好效果。

  • 汉朝治理黄河:
    秦汉时期,因为森林破坏严重,黄河开始泛滥。汉武帝时,黄河下游决口,汉武帝发动数万人抢修,还亲临现场,命令文武官员参与堵塞决口。东汉时,汉明帝命令水利专家王景治理黄河,使黄河下游两岸被淹没的土地又成为了良田。
  • 2016-05-17 | 0

    [ 数学 ] 已知x,y∈[-π4,π4],a∈R,且x3+sinx-2a=04y3+12sin2y+a

    已知x,y∈[-
    π
    4
    π
    4
    ],a∈R
    ,且
    x3+sinx-2a=0
    4y3+
    1
    2
    sin2y+a=0
    ,则cos(x+2y)=______.

    2016-05-17 | 0

    [ 数学 ] 一个直角三角形的三条边长度分别是10厘米、8厘米和6厘米,它的面积是( )A.48平方厘米

    一个直角三角形的三条边长度分别是10厘米、8厘米和6厘米,它的面积是(  )
    A.48平方厘米B.40平方厘米C.24平方厘米D.30平方厘米

    2016-05-21 | 0

    [ 数学 ] 红花3朵;黄花2朵;白花4朵.(1)红花占这束鲜花的几分之几?(2)黄花与白花共占这束鲜花

    红花3朵;黄花2朵;白花4朵.
    (1)红花占这束鲜花的几分之几?
    (2)黄花与白花共占这束鲜花的几分之几?

    2016-05-21 | 0

    [ 语文 ] 下列各组词语,没有错别字的一组是 A.更迭 恻隐之心 黄粱美梦 桃李不言,下自成溪 B.社

    下列各组词语,没有错别字的一组是
    A.更迭  恻隐之心  黄粱美梦  桃李不言,下自成溪
    B.社稷  没精打采  披星带月  盛名之下,其实难副
    C.端详  坐收鱼利  肺腑之言  一言既出,驷马难追
    D.宣泄  察言观色  出类拔萃  他山之石,可以攻玉

    2016-05-26 | 0

    [ 语文 ] 阅读下面的文字,简要概括油价猛涨的原因。 国际市场原油价格上周以来一涨再涨,屡创新高。 国

    阅读下面的文字,简要概括油价猛涨的原因。
      国际市场原油价格上周以来一涨再涨,屡创新高。
      国际能源机构发布报告说,世界主要工业国家上个月的原油商业库存已降到5年来的平均值以下。同时北半球尤其是美国进入冬季,对取暖用燃料的需求将大幅度增加。而最近一段时间,美元兑许多国家的货币比值都已创下多年来的最低,而自从美联储9月18日降息以来,美元的下跌趋势越来越快。分析人士认为,美国政府在有意放任“弱势美元”,以此刺激出口率的增长。
    答:_______________________________________________

    2016-05-27 | 0

    [ 英语 ] Can you make a model plane”  “_______. It is

    Can you make a model plane?”  “_______. It is easy.”
    A.Yes, I can.B.No, I can’t.
    C.Yes, I am.D.No, I am not.

    2016-05-28 | 0

    [ 英语 ] _______he was laid off last year ______ how s

    _______he was laid off last year ______ how serious the economic crisis was.
    A.Not until…he realized B. It was not until… when he realized
    C.It is not until…that did he realizeD.It was not until …that he realized

    2016-05-29 | 0

    [ 英语 ] DSure, it’s good to get along with your teach


    D
    Sure, it’s good to get along with your teacher because it makes the time you spend in the classroom more pleasant.
    And yes, it’s good to get along with your teacher because, in general, it’s smart to learn how to relate to the different types of people you’ll meet throughout your life.
    But really, there’s one super-important reason why you should get along with your teacher. When you do, “learning bursts right open,” says Evelyn Vuko, a longtime teacher who writes an education column called “Teacher Says” for the Washington Post newspaper.
    In fact, kids who get along with their teachers not only learn more, but they’re more comfortable asking questions and getting extra help. This makes it easier to understand new material and do your best on tests. When you have this kind of relationship with a teacher, he or she can be someone to turn to with problems, such as problems with learning or school issues, such as bullying(欺负人).
    As a kid in a primary or middle school, you’re at a wonderful stage in your life. You’re like a sponge(海绵), able to soak up lots of new and exciting information. On top of that, you’re able to think about all this information in new ways. Your teacher knows that, and in most cases, is very excited to be the person who’s giving you all that material and helping you put it together. Remember, teachers are people, too, and they feel great if you’re open to what they’re teaching you. That’s why they wanted to be teachers in the first place --- to teach!
    Some kids may be able to learn in any situation, whether they like the teacher or not. But most kids are sensitive to the way they get along with the teacher, and if things aren’t going well, they won’t learn as well and won’t enjoy being in class.
    67. In the passage, the teacher mainly talks about _____.
    A. how to get along well with teachers
    B. the importance of a good relation with teachers
    C. how much the students are expected of to get along with teachers
    D. how to make the time in the classroom more pleasant
    68. “Learning bursts right open” in the third paragraph really means _____.
    A. learning becomes easier for you at once     
    B. you find an opening to learning     
    C. there’ll be more problems with learning     
    D. there’ll be no problems with learning.
    69. According to the passage, which of the following offers the best reasoning?
    A. You are getting on well with your teachers, so you have more questions than others.
    B. You find it comfortable to ask questions, so you can build a good relationship with teachers.
    C. You have a good relationship with teacher, so you can turn to him/ her when in trouble.
    D. You are in trouble, so you can build a good relationship with teachers.
    70. Which of the comments is FALSE on teachers and their work according to the passage?
    A. Teachers are exited even if you wouldn’t like to accept their teaching.
    B. Teachers sometimes have the same feelings as students do.    
    C. Though few there are still some students who can learn even if they don’t like the teacher.  
    D. Having a bad relationship with your teachers does more or less harm to your studies.

    2016-05-29 | 0