总习题一
1( 在“充分”、“必要”和“充分必要”三者中选择一个正确的填入下列空格内(
(1)数列{xn}有界是数列{xn}收敛的________条件( 数列{xn}收敛是数列{xn}有界的________的条件(
(2)f(x)在x0的某一去心邻域内有界是
存在的________条件(
存在是f(x)在x0的某一去心邻域内有界的________条件(
(3) f(x)在x0的某一去心邻域内无界是
的________条件(
是f(x)在x0的某一去心邻域内无界的________条件(
(4)f(x)当x(x0时的右极限f(x0()及左极限f(x0()都存在且相等是
存在的________条件(
解 (1) 必要( 充分(
(2) 必要( 充分(
(3) 必要( 充分(
(4) 充分必要(
2( 选择以下题中给出的四个结论中一个正确的结论(
设f(x)(2x(3x(2( 则当x(0时( 有( )(
(A)f(x)与x是等价无穷小( (B)f(x)与x同阶但非等价无穷小(
(C)f(x)是比x高阶的无穷小( (D)f(x)是比x低阶的无穷小(
解 因为
(令2x(1(t( 3x(1(u) (
所以f(x)与x同阶但非等价无穷小( 故应选B(
3( 设f(x)的定义域是[0( 1]( 求下列函数的定义域(
(1) f(ex)(
(2) f(ln x)(
(3) f(arctan x)(
(4) f(cos x)(
解 (1)由0(ex(1得x(0( 即函数f(ex)的定义域为(((( 0](
(2) 由0( ln x(1得1(x(e ( 即函数f(ln x)的定义域为[1( e](
(3) 由0( arctan x (1得0(x(tan 1( 即函数f(arctan x)的定义域为[0( tan 1](
(4) 由0( cos x(1得
(n(0( (1( (2( ( ( ()(
即函数f(cos x)的定义域为[
]( (n(0( (1( (2( ( ( ()(
4( 设
(
(
求f[f(x)]( g[g(x)]( f[g(x)]( g[f(x)](
解 因为f(x)(0( 所以f[f(x)](f(x)
(
因为g(x)(0( 所以g[g(x)](0(
因为g(x)(0( 所以f[g(x)](0(
因为f(x)(0( 所以g[f(x)]((f 2(x)
(
5( 利用y(sin x的图形作出下列函数的图形(
(1)y(|sin x|(
(2)y(sin|x|(
(3)
(
6( 把半径为R的一圆形铁片( 自中心处剪去中心角为(的一扇形后围成一无底圆锥( 试将这圆锥的体积
表
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为(的函数(
解 设围成的圆锥的底半径为r( 高为h( 依题意有
R(2((()(2(r (
(
(
圆锥的体积为
(0(((2()(
7( 根据函数极限的定义证明
(
证明 对于任意给定的((0( 要使
( 只需|x(3|((( 取(((( 当0(|x(3|((时( 就有|x(3|((( 即
( 所以
(
8( 求下列极限(
(1)
(
(2)
(
(3)
(
(4)
(
(5)
(a(0( b(0( c(0)(
(6)
(
解 (1)因为
( 所以
(
(2)
(
(3)
(
(4)
(提示( 用等价无穷小换)(
(5)
( 因为
(
(
所以
(
提示( 求极限过程中作了变换ax(1(t( bx(1(u( cx(1(v(
(6)
( 因为
(
(
所以
(
9( 设
( 要使f(x)在(((( (()内连续( 应怎样选择数a?
解 要使函数连续( 必须使函数在x(0处连续(
因为
f(0)(a(
(
(
所以当a(0时( f(x)在x(0处连续( 因此选取a(0时( f(x)在(((( (()内连续(
10( 设
( 求f(x)的间断点( 并说明间断点所属类形(
解 因为函数f(x)在x(1处无定义( 所以x(1是函数的一个间断点(
因为
(提示
)(
(提示
)(
所以x(1是函数的第二类间断点(
又因为
(
(
所以x(0也是函数的间断点( 且为第一类间断点(
11( 证明
(
证明 因为
( 且
(
(
所以
(
12( 证明方程sin x(x(1(0在开区间
内至少有一个根(
证明 设f(x)(sin x(x(1( 则函数f(x)在
上连续(
因为
(
(
(
所以由零点定理( 在区间
内至少存在一点(( 使f(()(0(
这说明方程sin x(x(1(0在开区间
内至少有一个根(
13( 如果存在直线L( y(kx(b( 使得当x(((或x(((( x((()时( 曲线y(f(x)上的动点M(x( y)到直线L的距离d(M( L)(0( 则称L为曲线y(f(x)的渐近线( 当直线L的斜率k(0时( 称L为斜渐近线(
(1)证明( 直线L( y(kx(b为曲线y(f(x)的渐近线的充分必要条件是
(
(
(2)求曲线
的斜渐近线(
证明 (1) 仅就x((的情况进行证明(
按渐近线的定义( y(kx(b是曲线y(f(x)的渐近线的充要条件是
(
必要性( 设y(kx(b是曲线y(f(x)的渐近线( 则
(
于是有
(
(
(
同时有
(
(
充分性( 如果
(
( 则
(
因此y(kx(b是曲线y(f(x)的渐近线(
(2)因为
(
(
所以曲线
的斜渐近线为y(2x(1(
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