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一、对教材的分析与思考
“点到直线的距离”是“坐标平面上的直线”一章的最后一节内容．作为直线方程和向量方法的应用，在上海教材中，点P（x0，y0）到直线l：Ax＋By＋C=0的距离公式的推导经过了以下过程：（1）作出点P到直线l的距离PQ；（2）利用向量的数量积以及｜PQ→｜=｜PQ→·n→｜/｜n→｜（其中｜n→｜是直线l的法向量），再利用Q点坐标满足直线l的方程，求出｜PQ→｜，得到公式d=｜ax0＋by0＋c/√a^2＋b^2｜．推导中有两个要点：一是应用数量积的几何意义计算两点之间的距离；二是应用“若点在直线上，则点的坐标满足直线方程”进行整体代换． 相似文献
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1．阅读理解问题例
1阅读下面的例题：
解方程x^2-｜x｜-2=0．
解：（1）当x≥0时,原方程化为x^2-x-2=0．
解这个方程,得x1=2,x2=-1（不合题意,舍去）． 相似文献
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罗增儒 《中学数学教学参考》2007,(10):33-36,39
2．2再思考避开k的讨论
正如k=0时｜AB｜没有取到最大值一样,k不存在时｜AB｜也没有取到最大值,因而,化解了“k是否为0的讨论”之后,我们继续思考“k是否存在的讨论”能不能也化解．一个自然的想法是,用直线方程的其他形式（如一般式,两点式等）代替直线方程的斜截式． 相似文献
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董长紫 《唐山师范学院学报》2010,32(2):32-34
主要利用直接截断法来讨论非线性薛定谔微分方程：
iu1＋uxx＋α0｜u｜^2u＋i[γ1uxx＋γ2｜u｜^2ux＋γ3（｜u｜^2）xu]=0
的精确解．借助于符号计算软件Maple,得到了此方程一些新的含Jacobi椭圆函数的精确解。 相似文献
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在R^N空间中,一类关于n=p且含有临界位势的P-Laplacian方程：-div（｜u｜^N-2u-μ｜u｜^N-2u/｜x｜^Nln^nR/｜x｜=λg（x,u）,x∈Ω,u=0,x∈δΩ 利用没有（PS）条件山路引理证明了上面问题的非平凡解的存在性． 相似文献
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1．如图1所示,从双曲线x^2/a^2-y^2/b^2=1（a〉0,b〉0）的左焦点F1引圆x^2＋y^2=a^2的切线,切点为T,延长F1T交双曲线右支于P点．若M为线段F1P的中点,O为坐标原点,则｜MO｜-｜MT｜= 相似文献
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刘妮 《西安文理学院学报》2008,11(1):18-20
设T为复可分的希尔伯特空间H上的有界线性算子,T-U｜T｜是它的极分解,则T,^T：｜T｜^1/2U｜T｜^1/2与^T^（＊）=｜T＊｜^1/2U｜T＊｜^1/2具有相同的非零Kato谱,而^T和^T（＊）具有相同约化点谱． 相似文献
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本文总结了4种含0子块行列式的计算,在此基础上,结合初等变换,对定理“两个同阶方阵之积的行列式等于两个方阵的行列式的积（即｜AB｜—｜A｜｜B｜）”给出了一种新的证明方法． 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献