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1.
向量a与b之间的夹角定义为分别等于a和b并且具有公共始点的两个向量之间的夹角(Fig.1).向量a乘以向量b的数量积定义为ab,它等于这两个向量的绝对值与它们夹角的余弦的乘积,即ab=|a||b|cosθ.数量积具有如下可由定义直接推出的性质:(1)ab=ba;(2)a~2=aa=|a|~2;(3)(λa)b=λ(ab); 相似文献
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☆基础篇诊断检测一、选择题1.下列说法正确的是()(A)平行向量就是与向量所在直线平行的向量.(B)长度相等的向量叫相等向量.(C)零向量的长为0.(D)共线向量是在一条直线上的向量.2.已知向量a与b反向,下列等式成立的是()(A)|a|-|b|=|a-b|.(B)|a+b|=|a-b|.(C)|a|+|b|=|a-b|.(D)|a|+|b|=|a+b|.3.给出下列命题:(1)如果λa=λb(λ≠0),那么a=b.(2)若a0为单位向量,a与a0平行,则a=|a|a0.(3)设a=λ1e1+λ2e2(λ1,λ2∈R),则当e1与e2共线时,a与e1也共线.其中真命题的个数是()(A)0.(B)1.(C)2.(D)3.4.将函数y=x2+4x+5的图象按向量a经过一次平移后,… 相似文献
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新版高一数学 (下册 )第五章第三节《实数与向量的积》中 ,介绍了平面两个向量共线定理 :向量 b与非零向量 a共线的充要条件是有且只有一个实数λ,使得b =λa.由此 ,可以得到下列推论 :推论 1 OA、OB是平面内两不共线向量 ,向量OP满足 :OP =a OA +b OB( a,b∈ R) ,则 A、P、B三点共线的充要条件是 a +b =1.证明 :( 1)若 a +b=1,则 A P =OP - OA =( a -1) OA +b OB =b( OB - OA ) =b AB,故 AP与 A B共线 ,从而 A、P、B三点共线 ;( 2 )若 A、P、B三点共线 ,则存在唯一实数λ,使得AP =λAB,即 OP - OA =λ( OB - OA … 相似文献
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人教A版必修四第94页介绍了平面向量基本定理:如果e1、e2是同一平面内的两个不共线向量,那么对于一平面内的任意向量e1、e2a,有且只有一对实数λ1、λ2,使a=λ1e1+λ2e2.平面向量基本定理指出,平面内任何向量都可以沿两个不共线的方向分解为 相似文献
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向量共线的充要条件是由实数与向量的积推出的,它是平面向量的基本定理的一种特殊情况,具体内容为:向量b与非零向量a共线的充要条件是有且只有一个实数λ，使得b=λa, 由于零向量与任一向量共线，故上述定理又可叙述为向量b与向量a共线的充要条件是：存在不全为0的实数λ1, λ2, 使得λ1a+λ2b=0, 它的逆否命题为：若向量a, b不共线，(a≠0, b≠0)，且λ1a+λ2b=0, 则λ1=λ2=0，这些结论可用来证明几何中三点共线与两直线平行等问题.举例说明如下： 相似文献
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刘绍周 《中学数学研究(江西师大)》2004,(11):38-39
我们已经知道:向量b与非零向量a共线的充要条件是有且只有一个实数λ,使得b=λa.由此我们可以得到从一个始端出发的三个向量的终端共线的充要条件(我们简称三点共线向量的推论式)即推论:向量a,b,c有公共起点,则三个向量终点在同一条直线上的充要条件是存在实数λ,μ,使得c=λa μb.且λ μ=1. 相似文献
8.
向量共线的充要条件是由实数与向量的积推出的,它是平面向量的基本定理的一种特殊情况,具体内容为:向量b与非零向量a共线的充要条件是有且只有一个实数λ,使得b=λa,由于零向量与任一向量共线,故上述定理又可叙述为向量b与向量a共线的充要条件是:存在不全为0的实数λ_(1),λ_(2),使得 相似文献
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高考命题注重知识的整体性、综合性 ,常在知识的交汇处设计试题 .高中新教材增加了平面向量这一新内容 ,由于平面向量既具有几何形式 ,又具有代数形式 ,因而它成为中学数学知识的一个交汇点 ,备受命题者的青睐 .平面向量与解析几何的结合将是高考命题的趋势 .本文通过例题说明用平面向量解决解析几何问题 ,使二者达到完美结合 .一、基本知识( 1)向量共线定理 :向量 b与非零向量 a共线的充要条件是有且只有一个实数λ,使得 b =λa.推论 :OA ,OB是平面内两不共线向量 ,对于向量OP总存在 a,b满足 :OP =a OA + b OB( a,b∈ R) ,则A、P、B… 相似文献
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张威 《中国教育研究与创新》2006,3(11):145-150
天保房地产开发公司根植于天津滨海新区。依托控股公司带来的资源优势，基于滨海新区列入国家发展战略部署的背景，在近年来取得了迅速的发展。但是随着国家一系列政策的出台，中国的房地产行业面临着一次大的重新洗牌过程，同时企业内部仍然存在着制度缺陷、管理不规范、流程不清晰、人员激励不足等各方面的问题，所以，天保房地产公司在面临着滨海新区良好发展机遇的同时，也面临着很大的挑战。如何在机遇与挑战并存的环境中，认真分析和评估企业的外部环境及内部资源与能力的优劣势，对企业内部的资源与能力进行积累与培养，制定相应的竞争与发展战略，引导企业的健康长远发展具有一定的必要性与迫切性。
本文从竞争战略的角度，综合分析天保房地产开发公司所面临的外部环境和内部条件，研究探讨天保房地产开发公司的发展战略框架，包括战略的指导思想、战略定位、战略目标及相应的实施措施，以期实现天保房地产开发公司的发展愿景和核心价值。 相似文献
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The experiment in which a candle is burned inside an inverted vessel partially immersed in water has a history of more than
2,200 years, but even nowadays it is common that students and teachers relate the change in volume of the enclosed air to
its oxygen content. Contrary to what many people think, Lavoisier concluded that any change in volume in this experiment is
negligible; moreover, the explanation relating oxygen consumption in the air with its change in volume is known to be wrong.
In this work we briefly review the history behind the candle experiment and its relationship with some typical erroneous explanations.
One of the key factors behind Lavoisier’s success was the use of experiments carefully designed to test different hypotheses.
Following these steps, we performed several closed volume experiments where the candle wick was replaced by a capillary stainless
steel cylinder supported and heated by a nichrome filament connected to an external power supply. Our recorded experiments
are displayed as web pages, designed with the purpose that the reader can easily visualize and analyze modern versions of
Lavoisier’s experiments. These experiments clearly show an initial phase of complete combustion, followed by a phase of incomplete
combustion with elemental carbon or soot rising to the top of the vessel, and a final phase where the hot artificial wick
only evaporates a white steam of wax that cannot ignite because no oxygen is left in the closed atmosphere. After either a
complete or incomplete combustion of the oxygen, our experiments show that the final gas volume is nearly equal to the initial
air volume. 相似文献
13.
徐振芳 《中学英语之友(高二版)》2008,(Z2)
秦二世时,丞相赵高野心勃勃,日夜盘算着要篡夺皇位。可朝中大臣有多少人能听他摆布,有多少人反对他,他心中没底。于是,他想了一个办法,准备试一试自己的威信,同时也可以摸清敢于反对他的人。 相似文献
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Easy Phonics带你学习自然拼读,让你学会字母的发音规律,正确地拼读单词。本期让我们继续来看看、读读、写写重读音节中包含字母a的单词,区分它们读短音short a-/e/,还是长音long a-/ei/。 相似文献
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Easy Phonics栏目带你轻松地学习自然拼读!在读读、听听、拼拼和玩游戏中,你将了解字母的发音规律,并正确地拼读单词。这一期,我们来学习元音字母a的短音(short a)和长音(long a). 相似文献
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从前,有一句话,叫做"吃得苦中苦,方为人上人".这句话被认为动机不纯,怎么可以做"人上人"呢?其实,对于"人上人"可以作不同的理解,一种理解是"骑在人民头上,作威作福",这种"人上人"当然不好;但也可以解释为比别人做更多的贡献,吃更多的苦,经过更多的挫折与困难而比一般人更成熟、更坚强,更知道怎么做人.实际上,对这句话应是作后一种理解的,因为这种"人上人"是与"苦中苦"联系在一起的. 相似文献
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张昭兵 《南京师范大学文学院学报》2009,(4):37-44
本文从毕飞宇小说中一再出现的镜、钟、影和胡琴的意向入手,考察毕飞宇小说的叙述人称、叙述速度、叙述结构和叙述意图。深入阐释＂我＂与＂他＂的分离与揉合,＂快＂与＂慢＂的交替与演变,＂是＂与＂非＂的分明与模糊,＂语言＂与＂沉默＂的相反而相成。 相似文献
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The concept of metacognition refers to one’s knowledge and control of one’s own cognitive system. However, despite being widely
used, this concept is confusing because of several reasons. First, sometimes it is not at all clear what is cognitive and
what is metacognitive. Second, researchers often use the same term, namely, “metacognition” even when they refer to very different
aspects of this complex concept. Alternatively, researchers may use different terms to indicate the same metacognitive elements.
Another foggy matter is the interrelationships among the various components of metacognition discussed in the literature.
This conceptual confusion regarding the concept of metacognition and its sub-components calls for in-depth theoretical and
conceptual clarifications. The goal of this article is to portray a detailed example of a conceptual analysis of meta-strategic
knowledge (MSK) which is one specific component of metacognition. This specific example is used to draw a general model for
conceptual analyses of additional metacognitive components. The approach suggested here is to begin with a clear definition
of the target sub component of metacognition, followed by a systematic examination of this sub component according to several
dimensions that are relevant to metacognition in general and to that sub component in particular. The examination should include
an analysis of how the details of the definition of the target sub-component refer to: (a) general theoretical metacognitive
issues raised by prominent scholars; (b) definitions formulated and issues raised by other researchers who have investigated
the same (or a similar) sub-component and, (c) empirical findings pertaining to that sub-component. Finally, it should be
noted that since metacognition is a relational rather than a definite concept it is important to situate the context within
which the conceptual analysis takes place. 相似文献
19.
吴佳颖 《英语大王(小学)》2014,(3):34-34
In spring, it＇s always warm and sunny. People like to go outing. ff＇s sunny today. The Blacks have a picnic in a park. There are many big trees and flowers in the park. They take lots of food with them. There is fruit, drinks, bread and so on. 相似文献