文档内容
第二章
一元函数微分学例2.1 函数 f (x)在(−1,1)有定义,且lim f (x) = 0,则( C ).
x→0
f ( x)
fN 9 Y .
(A)若lim = 0,则 f (x)在 x = 0可导; R (31
: =
x→0 x
f ( x)
(B)若lim = 0,则 f (x)在 x = 0可导; S2(1 fix [
= =
x2
x→0
f ( x)
(C)若 f (x)在 x = 0可导,则lim = 0;
x→0 x
f ( x)
(D)若 f (x)在 x = 0可导,则lim = 0.
x2
x→0
(c) (D) fix Strc]E = ONES = fio = Me to fix = 0
.
fix-fro
M
fix My
=
=
#0 X j
-finf =
fix
I
=
M
c
=>
=
m
=>
↓
↓
O
C
AFO
O
#Fas例2.2 设奇函数 f (x)在 x = 0处可导,则函数
f ( x)( x + sin x)
, x 0
F(x) = x 在 x = 0处( D ).
0, x = 0
(A) 不连续 (B) 不可导
(C) 可导且F(0) = 0 (D) 可导且F(0) = 2 f (0)
flol
f
: o
: =
f(x
Mix
SmX) fix
=
IMEN + =
: +
X #
f(0)
F(d) FINE L
=2 = 0 = . X =f. XSM is
Fio Fi-Fol fix
M 8 (xism
-
= Um
O
=
X2
Y
fix
f fil-f
M b
m
= + 2
=
*
X
fir
2
=f (e2x − 1) − 1
例2.3 设 f (x)一阶可导且 f (0) 0,且 f (0) = 1,则lim
ln f ( x)
x→0
__________.
.
=
M
(n [1 f(x) 1)
+ -
fil-fi
fiel M fid
M
= = .
.
X - o
2
fix
2
= =
.
fixax2 + bx + c, x 0
例2.4 已知 f ( x) = 在 x = 0处有二阶导数, 试确定参数
ln(1 + x), x 0
a,b,c的值.
4
fix *
To
: =
fix E Of I
-
fio fill
fio
- = ( = 0 = o
,
: C = 0
fIN0(x =
Bit
· =
fin
To LES
:↑
fix
#J 2axth
X0 =
,
x0AJ fix i
, =
, fi Mfn
fix = fixb 1 ,
= =
"fix 92ax + 1 x
= ,
-
. 2a = -1 : a
1 X = 0 =
&
X >
ItX
fix-fo s
f1(d A Hm 2ax + 1 - 1
= = 2a
=
X - 8 x)0 X
I
fix-fo
find run i um - I *
m
= 1+X -
=
= 1
x+jt =
* X ( +x)
X -=例2.5 设 f (x)为周期为 5 的连续函数,它在 x = 0的某个邻域内满足:
f (1+ sin x) − 3 f (1− sin x) = 8x + o(x)
其中o(x)是当 x → 0时比 x 高阶的无穷小量, 且 f (x)在 x = 1处可导, 求
曲线 y = f (x)在点(6, f (6))处的切线方程.
: FIN E
:hm IfCHSmX) 3 fU-smx)) My EXTON]
- =
Xtr
f() fill
-3 0
=> =
fill
=> = rfitsmx-fi-sIfcsmx-fu
20
M mus + 0(X)
=>
#0
ShX
ShX
fl
flitsmx-
fli-smx-fl
Mr M pur 8X +ox)
=> 3
+
=
# 0 &
SmX SmX
-
f(6) fill
=> fil + 3 fix = 8 : = = o
f(6)
fill
fill = = 2
4 S
=> =
f(6)
(6 IT SEE
~
fill .
=> 2
=
* fix A B 5 : y - 0 = 2(X - 6)
fix A 5 y
. 2X 12
: = -
.例2.6 设函数 f (x), g(x)在(−,+)上有定义,且满足
f (x + y) = f (x)g( y) + f ( y)g(x), f (0) = 0, g(0) = 1, f (0) = 1, g(0) = 0.
试证明对一切 x , f (x)均可导,且 f (x) = g(x).
fix Un fixTox-fit) fix.glx flax 9-f
# Men +
= -
8X+0 -X
6X
flox
fix [910x) 1 + 9
me . - .
=
-Xo -X
910x-90 flox
-
fix
he Me
9
= . +
.
-X
f(x
= 90) 9141 fi0) 9(x)
. + · =例2.7 设函数 y = y(x)是由方程 y3 + xy + y + x2 = 0满足 y(0) = 0确定的连
x
y(t)dt
续二阶可导的函数,求lim 0 .
x3
x→0
In
Hat
YYYY
M
v X3
0x5X
y x y 44)
+ xy + y + = =
,
=> 3y y + y + x - y + y + 2x = 00X =0 . y = 0(x = yi) = 0
.
#IFE XcF* Y YIN %1 Y
= =
,
,
Jy(y'p 342 %" 2y1 %" y"
=> + . + + x . + + 2 = 02X = 0 . 4 =0 , Yir) = oft
=
Y T -5
-2
:
= ..↑
例2.8 设 f (x) = (1+ 2x)ln(1+ 2x),计算 f (2022)(0).
T ER
:
35-
(022) (2021)
2022)
In Go2 In
f(x) (2: C + 2x)
.
C + 2x)
+ ·
2
.
(1 +2x)
=
22
2 +
2x)]
(H
[In (1
+ = =
2 +2x)
(t2X
2x)]" ? 2x32 2x)]" 3 >
[m (1 +
=
2 (1)
·
(1 + [In ( +
=
2
·
( 1)
·
(-2)
·
C +2x)
"
mC -
2x) 2 ? () .. . . ( - (n - 11) (H2X) 2 ! ()* (n +) !
~ + = =
( 2x)"
+
(2022)
?
2202
(1) !
2021
fix (H 2x) . 22021
: + · !
- = + 2022 2 . 2020
. .
( 2x(2022
+
[ (2021
+2x?
for 2202
(1) !
2011
· 2021
(H2x)
· 2 !
+ 2022 2 . 2020
. .
( 2x(2022
+
[ (2021
+2x
flor 22022021 2202-2020
!
- + 2022 !
.
22022
2021 2020 ! + 2022
2202?
2020 !
=- . .
22022
!
2020
=> , 88
10例2.8 设 f (x) = (1+ 2x)ln(1+ 2x),计算 f (2022)(0).
Effor
33 = fix fla fir 0 (222
= + . X + +
!
2022
f(x)
= (1 + 2x) - (n(1 + 2x)
= (x 5(2x
(2x %
= (H + 2x) . - + +. )
...
*
x
=..... 2022
(x)
- ...
fo 2022
2
-'
=.... 240?X 2022
=
+...
2022 ! 2021 x2022
I flor 2022020
22022 2022 ~
y
= - ... !
2021 X 2012例2.9 设 f (x) = (x − 1)5e−x ,求 f (10)(1)
* *)
35 - fin Ci (x-1(* ) (16 ! (x1
51x-11
= . + .
. (x-11" ** 1 8 ? *)
( 20 ( ( 60 (x-11 (E-X(
+ . . + ·
1
*
->
20120
(x+1 · (
-X(
+ ( : 120
(eX)51
.
f !
( ( -eY) 10
x et)
: 10 (
= . T . . -
x= 1
5 !.
!
10 +
et
-
= e 30240
· = - .
5!例2.9 设 f (x) = (x − 1)5e−x ,求 f (10)(1)
(5 f()( = X 1 5 (( t+ ) Et -t
=: + e g(t)
. = . =
t
90
9 (t) 9 o
= , % + + +. + +
tet + - +)
+ t(1
9(t) ( t) o(t)
= e = e + + + +
ett +"
+...
+...
= -
gib
g
. e -Get fi -Fet
:
= =
I -
:
10&
例2.10 设 y = f (x)是区间[0,1]上的任一非负连续函数.
( )
(1)试证存在 x (0,1),使得在区间0, x 上以 f x 为高的矩形面积,等
0 0 0
于在x ,1上以 y = f (x)为曲边的梯形面积.
0
( X0fixd 16 i
fitidt
[T] EPGEEXO =
:
,
fixe 1x fitat
= x0 = 0
-
Xf(x-l
FNxd , F fitnt #
35 : = 0 =
- ,
F10) -1! fieldt F(ll full
< = > 0
=
fixo 1 * fitidt (X fitat)'(x
35 == EX0 + = 0 =
=xo
= 0
& / fat
FI X Fidlo Fill
= = -
, , ,2 f ( x)
(2)又设 f (x)在区间(0,1)内可导,且 f (x) − ,证明
x
( 1 ) 中的 x
0
是唯
一的.
fixo 1x fitat
x0 = 0
-
Pl9N
& X fin-1 fit at 0
91H =
= ,
9 fin fix f(x) fix f(x)
x = + X + = X + 2
x( 2) f(x)
> 2 = 0
- +
↑
9
:
&R-is
: 9(o) = 0 Xo ,例2.11 设 f (x)在[a,b]连续,在(a,b)可导,证明在(a,b)内至少存在一点
f () − f (a)
使得 = f ().
b −
[ FT) = < f 15)-f(al = (b - 5) fiz) < ) f(3)-f(a) + (5 - b) fig) = 0
-f(u)
FIs) . F() (x b) (fix)
=
E = 0 -
fix-f(a) f
Fix (x b)
= + -
FN) (fix -(f) F(al F(b)
it = = (b) = 0 = 0
.
,
-↑
x
2
例2.12 设函数 f (x) = et dt ;(1)证明:存在(1,2),使得
1
2
f () = (2 −)e .
es 2)e
( , et at
f(s)
(3-2) (5
NET) : + = 0 < + - = 0
.
/ etat *
Fl Fi
35 -i = 0 = + (x-2 e
, ·
/ etat
,
Fill -eco F(2 = > o
=
.
at)'
)
=((X 2)) Yet (x / etat
3 F(x
(x -2)
= = - =3 = 0 , = .
, ,
175
.
F(2)
F(l
= 0 = -
.2
(2)证明:存在(1,2),使得 f (2) = ln 2e .
en fixe
f12) <
EE) IAFT
:
= ,
In2 it = Inx
.
/2 MI InX EF E E Me (12)
EE
: = ,
er
fin) f12l-ful f(2)
o
-
= => -
t
gin) 9121-911 In2 0
-
F
=> er
n
= .
例2.13 设函数 f (x)在 0, 上连续,且 f (x)dx = 0, f (x)cos xdx = 0,
0 0
试证:在(0,)内至少存在两个不同的点 , ,使 f ( ) = f ( ) = 0.
1 2 1 2
( fN ax f(i) f(sl
1 : = x . = 0 = =o
& fil f(52)
losXdX = - losE = 0
-
⑳
/
FI
=ofInt EPEESE Fil Er
2 = =0
:
,
/ to
GEH FIN "fitut
: =
,
=
F(0 fittat
Fix
= 0 0
=
,2)
fiN
XaX = 0
.
in fixcoxaX FA
losX 1?
F-Saxax
= +
.
↑ ↓
1? flat
Fo
F(x) = 0 =o
=
,
(FM Saxax
! ficoax
: = · 7) FIX) . SmXo =0 Y((0 , 2)
,
F(xd
0
: =
: F(0) F(xd) = FIX) = 0
=
- u
Fil fIsEr FErl fIErI
= = =O例2.14 已知 f (x)在[0,1]上连续,在(0,1)内可导,且 f (1) = 1, f (0) = 0,证明
在(0,1)内至少有一点,使得e−1 f () + f () = 1.
e5 [ f(3) fig)]
I #11) : + = e
f(x)
(et
(x
E e
=
fIN
GERA : / FIX et #JE EEE (0 1)
= .
. .
.
F(1) Fros
[F(sl -
ecfisi
fiel
= => eTo
+
=
e
1 - 0 =例2.15 已知函数 f (x)在区间[a,+]上具有 2 阶导数, f (a) = 0, f (x) 0,
f (x) 0,设b a,曲线 y = f (x)在点(b, f (b))处的切线与 x 轴的交点是
f(b))
(b
( ) ·
x ,0 ,证明a x b. .
0 0
i
f( b)) +RESTE 4-fIbl f'(b) (x b)
LEHA (b : = . -
: ,
S
f(b) Yo
&
y
=0 = Xo b
=
-
f'(b)
fix fin ↑ fibl f(al F
= co : < = 01 78
,
b
Xo <
i
·
f(b) f(b)
Es b b
JeiE Xoca - > a => - ac
f(n)
f(D)
- f(n)
f(b)
f()
f(D)
↳
< =
b a
-E
FEIGHE ESE (a b)
It
.
,
f(b)-fal f(b)
fis)
= =
b b a
-a -
fin co fin ↑
:
&
f(b)
f()
fin)
: > =
b -a
f(b)
b
: - a >
f'(k)
b-flb
: .. Xo >
a
, ·
f(b)