2021年高等数学电子版.pdf
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1、.-.word.zl-第一章极限与连续第一节数列的极限一、数列极限的概念按照某一法则,对于每一个Nn,对应一个确定的实数nx,将这些实数按下标n从小到大排列,得到一个序列,21nxxx称为数列,简记为数列nx,nx称为数列的一般项。例如:,1,43,32,21nn,2,8,4,2n,21,81,41,21n,)1(,1,1,11n,)1(,56,43,34,21,21nnn一般项分别为1nn,n2,n21,1)1(n,nnn 1)1(数列nx可看成自变量取正整数n的函数,即)(nfxn,Nn设数列nnxnn1)1(,来说明数列nx以 1为极限。为 使100111)1(|1|1nnnxnn,只
2、需 要100n,即 从101 项 以 后 各 项 都 满 足1001|1|nx,为使100000111)1(|1|1nnnxnn,只需要100000n,即从 100001项以后各项都满足1000001|1|nx,为使nnnxnn11)1(|1|1(是任意给定的小正数),只需要1n,即当1n以后,各项都满足|1|nx。令1N,当Nn时,1n,因此有|1|nx,即任意给定小正数,总存在正整数1N,当Nn时的一切nx都满足|1|nx,则定义:设nx为一数列,如果存在常数a,对于任意给定的正数(不论它多么小),总存在正整数N,使得当Nn时的一切nx都满足不等式|axn则说常数a是数列nx的极限,或者说
3、数列nx收敛于a,记为axnnlim或axn)(n如果不存在这样的常数a,则说数列nx没有极限,或者说数列nx发散。|精.|品.|可.|编.|辑.|学.|习.|资.|料.*|*|*|*|欢.|迎.|下.|载.第 1 页,共 17 页.-.word.zl-数列nx以a为极限的几何意义:任意给定的正数,总存在正整数N,当Nn时的一切nx,有|axn即axan或),(aaxn也就是当Nn的一切nx都落在a的邻域),(aU,在),(aU的外边至多有N项(图)1xNxa1Nxa2Nxa例 1 证明数列,1,43,32,21nn的极限为1。证明:分析:为使11|nnaxn,只需要11n,或11n,即11n
4、证明:任意给定小正数,取11N,当Nn时的一切nx满足1111|1|nnnxn因此,11limnnn例 2 已知2)1()1(nxnn,证明数列nx的极限是0。分析:为使0)1()1(|2naxnn,只需要2)1(1n,由于11)1(1)1(122nnn,故11n时,即11n,或11n时2)1(1n。证明:任意给定小正数,取 11N,当Nn时的一切nx满足11)1(10)1()1(|0|2nnnxnn因此,0)1()1(lim2nnn例 3 设1|q,证明等比数列,112nqqq的极限是0。证明:任给0(设0),由于11|0|0|nnnqqx为使|0|nx,只需11|0|nnqq,解得ln|l
5、n)1(qn,或|lnln1qn。故取|lnln1qN,当Nn时,有11|0|0|nnnqqx因此,0lim1nnq。二、收敛数列的性质|精.|品.|可.|编.|辑.|学.|习.|资.|料.*|*|*|*|欢.|迎.|下.|载.第 2 页,共 17 页文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:C
6、L4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7
7、W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10
8、 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8
9、N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3
10、 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7
11、Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8
12、文档编码:CL4Q8N7W10M10 HP4H8N5K9L3 ZU1V7Q4S1U8.-.word.zl-定理 1(极限的唯一性)如果数列nx收敛,则它的极限是唯一的。证明:反证法:如果axn,bxn,不妨设ba。取2ab。由于axn,存在1N,当1Nn时,2|abaxn;又由于bxn,存在2N,当2Nn时,2|abbxn。取,max21NNN,则当Nn时,2|abaxn,2|abbxn,由2|abaxn得2baxn,由2|abbxn得2baxn,矛盾,故必须ba。例 4 证明数列1)1(nnx(,2,1n)是发散的。对于数列nx,如果存在正数M,使得对于一切nx,有Mxn|,则说数列nx是有
13、界的;否则,则说数列nx是无界的。定理 2(收敛数列的有界性)如果数列nx有极限,则数列nx一定有界。证明:注意到|aaxaaxxnnn,可证明定理2。定理 3(收敛数列的保号性)如果axnnlim,且0a(或0a),则存在正整数N,当Nn时的一切nx,有0nx(或0nx)。证明:取2a即可证明定理。推论如果数列nx从某项起有0nx(或0nx),且axnnlim,则0a(或0a)。对于数列nx,从中抽取1nx,2nx,knx,称为数列nx的一个子数列。定理 4 如果数列nx收敛于a,则数列nx的任何子数列都收敛,且收敛于a。第二节函数的极限一、函数极限的定义1自变量趋向于无穷大时函数的极限数
14、列 是 特 殊的 函 数,如1)(nnnfxn,,2,1n,且n时,1nx,考 虑函 数1)(xxxfy,是否有x时,1)(xf?任 意 给 定 小 正 数,为 使|11|1)(|xxxf,只 要|11|x,即1|1|x。由 于1|1|xx,即11|x即可。任给0,存在正数11X,当Xx|时,对应的函数值)(xf满足|11|1)(|xxxf即当x时,)(xf以 1为极限。定义 1 设函数)(xf当|x大于某一正数时有定义。如果存在常数A,对于任意给定的正数(不论|精.|品.|可.|编.|辑.|学.|习.|资.|料.*|*|*|*|欢.|迎.|下.|载.第 3 页,共 17 页文档编码:CB5S
15、5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S1
16、0T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6
17、R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB
18、5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6
19、S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5
20、W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:
21、CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9.-.word.zl-它多么小),总存在正数X,使得x满足不等式Xx|时,对应函数值)(xf满足|)(|Axf则说常数A为函数)(xf当x时的极限,记为Axfx)(lim或Axf)((当x)Axfx)(lim:0,0X,当Xx|时,|)(|Axf。例 1 证明03limxx。分析:
22、为使|03|x,只要|3|x,即|3x,或3|x。证明:0,3X,当Xx|时,|3|03|xx,因此03limxx。Axfx)(lim的几何解释:0,0X,当Xx|时,|)(|Axf即Axf)(或AxfA)(如图所示:如果0,0X,当Xx时,|)(|Axf,则说x时,Axf)(,记为Axfx)(lim;如果0,0X,当Xx时,|)(|Axf,则说x时,Axf)(,记为Axfx)(lim显然,Axfx)(limAxfx)(lim,Axfx)(lim例如:xxxf|)(,有1)(limxfx,1)(limxfx。2自变量趋向于有限值时函数的极限例 1,12)(xxf,2x时,5)(xf;例 2:1
23、1)(2xxxf,定义域为1x,但1x时,2)(xf;任 意 给 定 小 正 数,为 使|42|512|)(|xxAxf,只 要|2|2 x,即2|2|x即可。任意给定小正数,为使|21)1)(1(|211|)(|2xxxxxAxf只要|1|x,即|1|0 x即可。定义 2 设函数)(xf在点0 x的某一去心邻域内有定义。如果存在常数A,对于任意给定的正数(不论它多么小),总存在正数,使得x满足不等式|00 xx时,对应函数值)(xf满足|精.|品.|可.|编.|辑.|学.|习.|资.|料.*|*|*|*|欢.|迎.|下.|载.第 4 页,共 17 页文档编码:CB5S5P2R4G3 HU6S
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25、6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:CB5S5P2R4G3 HU6S10T1U2Y4 ZJ5W6R2D5J9文档编码:C
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