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北大版高数第十章习题解答.pdf

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n+p n+p cos k cos n n(n+1) Pn=1 cos n n(n+1) Pn=1 1√n Pn=1 n+p Pk=n+1 n+p Pk=n+1 1 k(k+1) = k+1 ) = 1 cos k k(k+1)| ≤ n+1 − 1 n+p+1 < 1 Pk=n+1 Pk=n+1 n+p ( 1 k − 1 k(k+1)| < 1 5êÆ61›S‰ SSS10.1 1.|^…Âñy²: (1)?ê ∞ Âñ. y. | n .é ?¿ε > 0, N = [ 1 ε ],n > Nž, | n < ε.d…Âñ, ?ê ∞ Âñ. (2)?ê ∞ Ñ. 1√k| ≥ p√n+p . NõŒ,n = p = N + 1ž, | y. .d…Âñ,?ê ∞ Ñ. (3)‡?ê ∞ an† ∞ bnÑÂñ,…3êN ,n ≥ Nžkan ≤ un ≤ bn,?ê ∞ unǑÂñ. an† ∞ y.é?¿ε > 0,ÏǑ?ê ∞ bnÂñ,¤±3N′ > N , n > N′ž, | bk| < ε.¡, uk| < ε.¤±?ê ∞ unÂñ. bk.¤± 2.®?ê ∞ anÂñ,?ê ∞ bn Ñ,¯?ê ∞ (an ± bn)ÄÂñ? ‰: Ñ.Ä ∞ (an ± bn)ǑÂñ. 3.äe?êÄÂñ. √k) = √n + 1− 1,3n → ∞ (√n + 1−√n).ÏǑ© n ž vk4,¤±?ê Ñ. (2n−1)(2n+1) .ÏǑ n žk4,¤±?êÂñ. 3n → ∞ n = 1,¤±?ê Ñ. n .ÏǑ lim Pk=n+1 | q N +1 2 ≥ 1√2 Pk=n+1 Pk=n+1 | Pn=1 Pk=n+1 n+p (√k + 1− (2k−1)(2k+1) = Pn=1 an ± 1 2k−1 − 1 2k+1 ) = 1 2 (1− 1 2n+1 ), Pn=1 Pn=1 ak| < ε, | Pk=n+1 ak ≤ Pk=n+1 Pn=1 bn = ± n+p Pk=n+1 n+p Pk=n+1 1√n Pn=1 n Pk=1 1 2 ( 1√k| ≥ ∞ Pn=1 (4) cos2 π n+p n+p Pk=1 1 (1) (2) n+p n+p uk ≤ Pn=1 ∞ Pn=1 1 Pk=1 Pn=1 Pn=1 Pn=1 Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 cos2 π n→∞ 1
n→∞ Pn=1 n→∞ Pn=1 Pn=1 n→∞ nun = 0. lim n→∞ (7) ∞ Pn=1 {S2n} {S2n+1} n+p Pk=n+1 S2n = lim n→∞ n√0.0001.ÏǑ lim n√0.0001 = 1,¤±?ê Ñ. 4.?ê ∞ un©SǑ {Sn}.en → ∞ ž † ÑÂñ… ñÓ‡~êA.y²?ê ∞ unÂñ. S2n+1 = A,¤±3N > 0, y.é?¿ε > 0,ÏǑ lim n > Nž, |S2n − A| < ε, |S2n+1 − A| < ε. n > Nž, |Sn − A| < ε.¤ ± lim unÂñ. Sn = A,?ê ∞ 5.?ê ∞ unÂñ,…un ≥ un+1 ≥ 0 (n = 1, 2, . . . ),y²: y.é?¿ε > 0,ÏǑ?ê ∞ unÂñ,d…Âñ,3N , n > Nž, 2 . n > Nž, (2n)u2n ≤ 2 uk < ε.¤± lim SSS10.2 1.?e?êñÑ5. 2n = π,?ê ∞ 4n .ÏǑ lim Âñ,¤±?êÂñ. Âñ,¤±?ê .ÏǑ lim ,?ê ∞ ñ. n√n = 1,¤±?ê Ñ. n√n .ÏǑ lim Ñ,¤±?ê Ñ. n = 4,?ê ∞ n2+4n−3 .ÏǑ lim .ÏǑ lim Âñ,¤±?êÂñ. 2 ,?ê ∞ (ln n)ln n .ÏǑ lim (3 − ln ln n) ln n = −∞,¤ ± lim n2 = 0.?ê ∞ Âñ,¤±?êÂñ. 3 ,d…{,?êÂñ. 3n .ÏǑ lim 2.?e?êñÑ5. Pn=1 / 1 n2 = lim n→∞ ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 1 n2 Pn=1 nqn tan 1 (2n + 1)u2n+1 ≤ (1 + 3n+1 n2 )− n+2 n2 ] = lim n→∞ Pn=1 Pn=1 1√2n3+1 / 1√n3 = 1√2 4n n2+4n−3 / 1 ∞ Pn=1 ∞ Pn=1 n→∞ ∞ Pn=1 ln[ n (ln n)ln n / 1 2n sin π 4n / 1 n (ln n)ln n / 1 2n+1 Pk=n+1 2n Pk=n+1 2n Pk=n+1 (n2+3n+1) n+2 2 (n2+3n+1) n+2 2 (5) e− 3 (7) n tan 1 (6) ∞ Pn=2 (1) (2) (3) (4) 1 n2 Pn=1 n n→∞ 1 1 4n 1 2n 1√n3 nun = 0. n→∞ 2n sin π 1√2n3+1 un < ε uk + nn nn n→∞ n→∞ n→∞ n→∞ uk < ε. n→∞ 2 = 1 n Pn=1 Pn=1 n→∞ 3n = 1 2
3(1 + 1 n→∞ n→∞ 1 n Pn=1 n5 n! 3n·n! 1 n→∞ n→∞ n! n→∞ n→∞ n→∞ 1000n n! (n!)2 n2 (3− 1 n (1) (2) (3) (4) (5) (6) (7) (8) 1 n1+1/n / 1 n )n = 1 (n+1)5 (n+1)! / n5 nn = lim n→∞ 3n+1·(n+1)! (n+1)n+1 / 3n·n! ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=2 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=2 nq n2 (3− 1 nq n 1000n+1 (n+1)! / 1000n n! .ÏǑ lim n! = 0,dˆ{,?êÂñ. 3n2 .ÏǑ lim 3n2 = +∞,?ê Ñ. nn .ÏǑ lim n )−n = 3e−1 > 1,dˆ {,?ê Ñ. n1+1/n .ÏǑ lim n = 1,?ê ∞ Ñ,¤±?ê Ñ. n )n .ÏǑ lim 3 ,d…{,?êÂñ. (ln n)n .ÏǑ lim (ln n)n = 0,d…{,?êÂñ. n! = 0,dˆ{,?êÂñ. .ÏǑ lim 4 ,dˆ{,?êÂñ. (2n)! .ÏǑ lim .ÏǑ lim 3 < 1,d…{,?êÂñ. n(ln n)p (p > 0).p > 1ž,È© Âñ,¤ ±?êÂñ.p = 1ž,È© Ñ,¤±?ê Ñ. Ñ,¤±?ê Ñ. 0 < p < 1ž,È© n(ln ln n)q (q > 0).ÏǑ lim Ñ,¤±?ê Ñ. (ln x)q = +∞.?ê ∞ unÂñ,?ê ∞ 3.y²:e?ê ∞ ǑÂñ.‡ƒ ¤ ,Á~ `².y.ÏǑ?ê ∞ un = 0,¤±S unÂñ,¤± lim k..un < M . n ≤ M un.d{,?ê ∞ Âñ. u2 Ñ. n )2Âñ, ∞ ‡ƒ ¤ ,~X?ê ∞ Ǒ 4.y²:e?ê ∞ † ∞ ÑÂñ,?ê ∞ Âñ.y.d^‡,?ê ∞ n)Âñ.d x(ln x)p = ln ln x|+∞2 x(ln x)p = (ln x)1−p 1−p x(ln x)p = (ln x)1−p 1−p n(ln n)1/2 = lim n→∞ (2n+2)! / (n!)2 ((n+1)!)2 (2n)! = 1 3n ( n+1 n )n2 = e n→∞ Pn=1 Pn=1|anbn|, (ln n)1/2 (ln ln n)q = 1 3n ( n+1 n )n2 1 n(ln ln n)q / lim x→+∞ |anbn| ≤ 1 2 (a2 n + b2 n), (an + bn)2 ≤ (an+bn)2, a2 n Pn=1 u2 n Pn=1 ∞ Pn=1 |an|n b2 n Pn=1 ( 1 Pn=1 1 n(ln n)1/2 (a2 n + b2 (9) (10) R +∞ 2 1 R +∞ 2 1 R +∞ 2 1 (11) ∞ Pn=3 nq 1 n→∞ 1 1 1 n Pn=1 |+∞2 1 Pn=3 Pn=1 {un} ∞ Pn=1 x1/2 n→∞ |+∞2 n→∞ Pn=1 Pn=1 u2 n 3
2(a2 n + b2 ∞ Pn=1 n→∞ (1) (2) Pn=1 ∞ Pn=1 Pn=1 n Pn=1 n Pn=1 ∞ Pn=1 unvn. |an|n Pn=1 (1) (un + vn); (2) Pn=1|anbn|, Pn=1 ∞ Pn=1 (un − vn); (3) n),¤±?ê ∞ n ,=Ñ? (an + bn)2ǑÂñ.bn = 1 Âñ. ê ∞ 5.y²:e?ê ∞ vnÑÂñ,¯e?êÄ Ñ? un† ∞ ‰. (1) Ñ,ÏǑun + vn ≥ un,Šâ{,?ê ∞ (un + vn) Ñ. (2) ,Xun = vn = 1 ž,?ê ∞ (un − vn)Âñ0. (3) , unvnÂñ. Xun = vn = 1 ž,?ê ∞ un Ñ. 6. lim nun = l,¥0 < l < +∞.y²?ê ∞ Âñ, ∞ nun = l > 0¿›Xn¿©Œžun > 0.¤±Œ±bun > 0.Ï y.Äk lim Âñ.ÏǑ lim n2 = l2,?ê ∞ Âñ,¤±?ê ∞ Ǒ lim ?ê ∞ Ñ,¤±?ê ∞ un Ñ. SSS10.3 1.äe?êÄÂñ?^‡Âñ„éÂñ? .ÏǑ ∞ Âñ,¤±?êéÂñ. (2n−1)p (p > 0).S ª 0,¤±T†?êÂñ.? …=p > 1žÂñ,¤±?êp > 1žéÂñ,Ä^‡ ê ∞ Âñ. n ln n .S ª 0,¤±T†?êÂñ.?ê ∞ Ñ,¤±?ê^‡Âñ. n .ª= n ,‡†?êÑ n / 1√n = 1,¤±?ê ∞ ñ,¤±?êÂñ. lim Ñ.¤± ?ê^‡Âñ. 32n+1 = 0.dˆ{, 3n2 .ÏǑ lim ?êéÂñ. Pn=1| (−1)n−1 { (−1)n 1√n − √n−1 ∞ Pn=1 ∞ Pn=1 Pn=1 (−1)n √n−1 3n2 = lim n→∞ n→∞ Pn=1 (n+1)! 3(n+1)2 / n! Pn=1 Pn=1 (−1)n n! 1 (2n−1)p } 1 n ln n Pn=2 ∞ Pn=1 | = ∞ Pn=1 (−1)n 1 (3) ∞ Pn=2 (4) ∞ Pn=1 (6) ∞ Pn=1 √n−1 n Pn=1 (−1)n−1 (2n)2 (−1)n+1 ∞ Pn=1 n→∞ 1 (2n−1)p (−1)n un/ 1 n = l, n→∞ n→∞ n/ 1 u2 1 n u2 n Pn=1 Pn=1 (2n)2 1 (2n)2 1 n2 u2 n Pn=1 n→∞ n+1 { 1 n ln n} 4
Pn=1 sin Pn=1 Pn=1 n (10) ∞ Pn=1 n Pn=1 (7) (8) un np Pn=1 { n n+1} n→∞ un 1 n sin π n / 1 ∞ Pn=2 ∞ Pn=1 π√n2+1+n / 1 n = π { 1 np } Pn=1 n (− π | tan ϕ n| n→∞| tan ϕ n|/ 1 n→∞ 2 < ϕ < π n sin π (−1)n 1 (−1)n+1 tan ϕ n = |ϕ|, sin(π√n2 + 1). sin(π√n2 + 1) = (−1)n sin π(√n2 + 1−n) = (−1)n sin n2 = π,¤±?êéÂñ. n .ÏǑ lim 2 ).ϕ = 0ž,?êwéÂñ.ÄT? ª 0,Ïd?êÂñ. lim êǑ†?ê,… ?êéÂñ. 2 ,?êéÂñ. ÏdT?êǑÂñ†?ê. lim 2.®?ê ∞ unÂñ,y²?ê ∞ np (p > 0)† ∞ n+1 unÂñ. unÂñ,dC{,? k.,ÏǑ?ê ∞ y.ê 9 ê ∞ † ∞ n+1 unÂñ. (0 < ϕ < 2π)p > 1žéÂñ,0 < p ≤ 1ž^‡Â 3.y²?ê ∞ ñ.y. (i)p > 1ž,?ê ∞ Âñ.d np ,?ê ∞ é cos kϕk.,d Âñ. (ii)0 < p ≤ 1.d ê ª 0,© n |ŽX{,?ê ∞ Âñ.ÓŒyϕ 6= πž,?ê ∞ Âñ. Ñ.ÏǑ d ?ê ∞ Ñ,¤±?ê ∞ ,?ê ∞ éÂñ. ?ê¡Š|ŽX?ê.y²§ke5Ÿ:e?ê ∞ 5./X ∞  ñ( Ñ),x > x0(x < x0)ž,?ê ∞ ǑÂñ( Ñ). k..dC{, y.?ê ∞ Âñ.x > x0ž,ê ?ê ∞ nx0 nx0−xÂñ. n unǑéÂñ. unéÂñ,y²?ê ∞ 6.?ê ∞ y. | 2n−1 ǑÂñ. n un| ≤ 2|un|,¤±?ê ∞ Âñ¿›X?ê ∞ SSS10.4 Pn=1 | ≥ cos2 nϕ | cos nϕ Pn=1 Pn=1|un| | cos nϕ np | ≤ 1 Pn=1 an nx = an nx0 ∞ Pn=1 Pn=1 2n−1 n |un| {nx0−x} an nx Pn=1 an nx Pn=1 1 np Pn=1 1 2np Pn=1 an nx0 Pn=1 1+cos 2nϕ 2np 1+cos 2nϕ 2np cos nϕ np Pn=1 cos nϕ np Pn=1 cos nϕ np Pn=1 cos nϕ np Pn=1 np np = { 1 np } Pn=1 Pn=1 an Pk=1 cos 2nϕ 2np π√n2+1+n . Pn=1 2n−1 5
3 π |x| > xn sin π 3 ) ∪ ( 1 1 xn sin π lim n→∞ (1) fn(x) = 1 (1) (2) (3) 1 3 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 1 2n−1 ( 1−x 1 xn sin π 2n+x2 , −∞ < x < +∞. lim n→∞ |fn(x) − 0| ≤ 1 (2) fn(x) = √x4 + e−n, −∞ < x < +∞. |x| ≤ 1 3n | ≤ 1 |x|n 3 , +∞). 1.e?êÂñ. | ln x| < 1ž?êÂñ,¤±ÂñǑ(e−1, e). (ln x)n.…= 1+x )n.…= 1−x 1+x ∈ [−1, 1)ž?êÂñ,¤±ÂñǑ(0, +∞). ž, 3n 6= 0,¤±?ê Ñ. 3n . 3n ,d{Œ,?êéÂñ.¤±Âñ ž, | 1 Ǒ(−∞,− 1 2.?eêS3¤««SÂñ5. . 2n ,… lim 2n = 0,¤±êS fn(x) = 0.d ñ. fn(x) = √x4 = x2.d . … lim 2 = 0,¤±êSÂñ. fn(x) = 0. (a)d . n2 ,… lim n2 = 0,¤±êS 3«(−l, l)Âñ. (b)xn = n, lim [f (xn) − 0] = ln 2¤±ê S3«(−∞, +∞)Âñ. ¤±êS . fn(x) = 1.xn = 1 n2 , lim Âñ. 3.?e?ê3¤««Âñ5. . |(−1)n √n n3/2 ,dM{,?êÂñ. n = 0,¤±?êÂñ. . | n3 ,dM{,?êÂñ. . | (−1)n √n x2+n2| ≤ n − xn+1 ( xn n+1 ), −1 ≤ x ≤ 1. k+1 )| = | xn+1 k − xk+1 ( xk n2 ), (a) −l < x < +l, (b) −∞ < x < +∞. √1+(x2+n2)3 , −∞ < x < +∞. x2+n2 , −∞ < x < +∞. e−n √x4+e−n+x2 ≤ e−n √e−n = e− n 2 , [f (xn) − 1] = − 1 2 |fn(x) − 0| ≤ x2 n2 < l2 (4) fn(x) = n2x 1+n2x , 0 < x < 1. ∞ Pn=1 ∞ Pk=n+1 ∞ Pn=1 √1+(x2+n2)3 | ≤ 1 ∞ Pn=1 sin nx sin nx x 1+4n4x2 , −∞ < x < +∞. n+1 | ≤ 1 n , 1 lim n→∞ (3) fn(x) = ln(1 + x2 |fn(x) − x2| = lim n→∞ e− n n→∞ (1) ∞ Pn=1 √n n2 = 1 (3) (4) lim n→∞ lim n→∞ l2 n→∞ n→∞ (2) 1 n→∞ n→∞ 6
1 n Pk=1 ∞ Pn=1 (6) (7) (5) x2 lim n→∞ | 1+nx ≤ 1 n , x2 (1+x)k = x x 1+4n4x2| ≤ 1 | , −∞ < x < +∞. sin x · sin kx| = | cos x 2 − cos(n + 1 2 )x]| ≤ 2, sin x·sin nx √n2+x2 , 0 ≤ x ≤ 2π. 1√n2+x2} { 2 · [cos x ∞ (−1)n−1x2e−nx2 Pn=1 ∞ Pk=n+1 (−1)k−1x2e−kx2 ∞ Pn=1 (1+x)n , −∞ < x < +∞. ∞ (1+x)n ≤ x Pk=n+1 ∞ Pn=1 1√n2+x2 ≤ 1 n , 4n2 ,dM{,?êÂñ. . 1 + 4n4x2 ≥ 4n2|x|,¤± n = 0,¤±?êÂñ. . Âñ0.Ï . n = 0,¤±êS Ǒ 1√n2+x2  n,… Šâ|ŽX{,?êÂñ. . | n = 0,¤±? êÂñ. 3−n sin 2nx3(−∞, +∞)¥Âñ,…këY 4.y²?êf (x) = ê.y. (i) |3−n sin 2nx| ≤ 3−n,ŠâM{,?ê ∞ 3−n sin 2nxÂñ. 3 )n,ŠâM{,?ê ∞ (3−n sin 2nx)′ Âñ. f (x)këYê. 3(−∞, +∞)¥Âñ,3?¿4« 5.y²?êg(x) = [−M, M ] (M > 0)Âñ,¿y²g(x)3(−∞, +∞)¥këYê. y. 3k | ≥ 2n+1 sin 1 > sin 1,¤±?ê (i)xn = 3n+1, 3(−∞, +∞)¥Âñ. (ii)x ∈ [−M, M ]ž, |2n sin x 3 )n.ŠâM{,? 34«[−M, M ]Âñ. ê ∞ 3 )n,ŠâM{,?ê ∞ 3n )′3 «(−∞, +∞)Âñ. g(x)3«(−∞, +∞)këYê. 6.y²?êζ(x) = 3?¿«[1 + δ, +∞)¥Âñ(δ > 0),¿y²? 3?¿«[1+δ, +∞)¥Âñ(δ > 0),Ñêζ(x)3(1, +∞)¥ ê ∞ këYê. (ii) |(3−n sin 2nx)′| = |( 2 | = x2e−nx2 ex2 +1 ≤ x2e−nx2 (iii) |(2n sin x 3n )′| = |( 2 3n| ≤ |2n · x 3n | ≤ M ( 2 3 )n cos 2nx| ≤ ( 2 3 )n cos x 3n | ≤ ( 2 ∞ Pk=n+1 | 2n sin x 3n Pn=1 ∞ Pn=1 1 nx ≤ e−1 n , lim n→∞ e−1 (2n sin x Pn=1 ∞ Pn=1 2n sin x 3n Pn=1 Pn=1 ln n nx Pn=1 1 lim n→∞ 2k sin xn 7
1 nx Pn=1 ∞ Pn=1 ( 1 nx )′ = x→0+0 ln n nx Pn=1 Pn=1 an nx Pn=1 ln n ln n ∞ Pn=1 ∞ Pn=1 nx ≤ 1 ∞ Pn=1 − ln n ∞ Pn=1 an nx = n1+δ ≤ M (ii) lim n→∞ nx ≤ ln n y. (i)x ∈ [1 + δ, +∞]ž, 1 n1+δ ,ŠâM{,?ê ∞ 3«[1 + δ, +∞)¥Âñ. nδ/2 = 0,¤±3M > 0, ln n nδ/2 < M . x ∈ [1 + δ, +∞]ž, n1+δ/2 ,ŠâM{,?ê ∞ 3«[1 + δ, +∞)¥Âñ. (iii)¤ã,3?¿«(1+δ, +∞), ζ(x)këYêζ′(x) = nx .¤±ζ′(x)3«(1, +∞)ëY. 8. ∞ 3[0, +∞)¥Âñ,¿k lim anÂñ.y²?ê ∞  n,… 1 an.y.x ∈ [0, +∞)ž, nx ≤ 1.d ∞ anÂñ,ŠâC 3[0, +∞)¥Âñ. lim {,?ê ∞ an.SSS10.5 1.e?êÂñŒ. 2 ,ÂñŒǑ2. n+1 = 0,ÂñŒǑ+∞. n )−n = e−1,ÂñŒǑe. 4 ,ÂñŒǑ4. 2.e?êÂñ«†Âñ. 3√n = 1,Âñ«Ǒ(−1, 1).x = 1ž?ê Ñ, x = −1ž†?êÂñ,¤±ÂñǑ[−1, 1). a ,Âñ«Ǒ(−a, a).x = až?ê Ñ, x = −až†?êÂñ,¤±ÂñǑ[−a, a). (2n+1)·(2n+1)! = 0,Âñ« ÂñǑ(−∞, +∞). ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 ∞ Pn=1 n )k · (1 + 1 (n+1)2n+1 / 1 n2n = 1 |x2n+3| (2n+3)·(2n+3)! / (n+1)2 (2n+1)(2n+2) = 1 (2n)! = lim n→∞ ((n+1)!)2 (2n+2)! / (n!)2 x2n+1 (2n+1)·(2n+1)! . nn = lim n→∞ n! = lim n→∞ xn nan (a > 0). nq 1 nan = 1 lim n→∞ lim n→∞ ∞ Pn=0 (−1)n Pn=1 ∞ Pn=1 (n+1)! (n+1)n+1 / n! (1) (2) (3) (4) ∞ Pn=1 ∞ Pn=1 lim x→0+0 an nx = xn n2n . lim n→∞ (n+1)k (n+1)! / nk an nx = ∞ Pn=1 xn 3√n . lim n→∞ nk n! xn. n! nn xn. (1) (2) (3) (1 + 1 1 (n!)2 (2n)! xn. lim n→∞ 1 3√n+1 / 1 lim n→∞ 1 nx 1 lim n→∞ |x2n+1| an nx Pn=1 x→0+0 8
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