INDETERMINATE
FORMS
OBJECTIVES:
• define, determine, enumerate the
different indeterminate forms of
functions;
• apply the theorems on differentiation
in evaluating limits of indeterminate
forms of functions using L’Hopital’s
Rule.
.
( )( )
( ) 2313-xlim
1x
3x1-x
lim
1x
3x4x
lim
:followsasnumeratorthefactorweexist,tolimit
theforandform,ateindeterminanislimitthe
0
0
11
3)1(4)1(
1x
3x4x
lim
1x
3x4x
limofitlimtheEvaluate:callRe
1x1x
2
1x
22
1x
2
1x
−=−==
−
−
=
−
+−
=
−
+−
=
−
+−
−
+−
→→→
→
→
2
1x
3x4x
lim,thus
2
1x
−=
−
+−
→
used.bewillRulesHopital'L'onTheoremslimit
saidtheevaluateToexample.secondthetoappliedbelonger
nocanproblemsprevioustheinappliedprincipletheObviously,
0
0
0
)0sin(
)0(2
)0(2sin
2x
2xsin
lim
2x
2xsin
limtheevaluatingconsiderusLet
0x
0x
===→
→
.
∞
∞
∞∞
∞⋅
∞
∞
1,,05.
and-4.
03.
:FormsSecondaryB.
2.
and
0
0
1.
:FormsPrimaryA.
:formsateindeterminofKinds
00
.
Theorem 3.6.1 (p. 220) L'Hôpital's Rule for Form 0/0
.
Applying L'Hôpital's Rule (p. 220)
Theorem 3.6.2 (p. 222) L'Hopital's Rule for Form ∞/∞
.
2x
2xsin
lim.1 0x→
EXAMPLE:
Evaluate the following limits.
( )
( )
( )
0
0
0
0sin
02
02sin
2x
2xsin
lim0x
===→
( )
( )
( )
( )
( )
10cos
2
02cos2
12
2x2cos
lim
2x
dx
d
2xsin
dx
d
lim
2x
2xsin
lim
:Rules'Hopital'LgsinuBy
0x0x0x
===
== →→→
1
2x
2xsin
lim
0x
=∴
→
.3ysin-y
3y-ytan
lim.2 0y→
( ) ( )
( ) ( ) 0
0
00
00
0sin3-0
03-0tan
3ysin-y
3y-ytan
lim0y
=
−
−
==→
( )
( )
( )
( )
( )
1
2
2
31
31
03cos-1
30sec
33ycos-1
13ysec
lim
3ysin-y
dx
d
3y-ytan
dx
d
lim
3ysin-y
3y-ytan
lim
:LHRBy
2
2
0y0y0y
=
−
−
=
−
−
=
−
=
−
== →→→
1
3ysin-y
3y-ytan
lim
0y
=∴
→
.
( )
( )2
4
x x4
2xsinln
lim.3
−ππ
→
( )
( )
( )
( )
( )
( )( )4x42
2x2cos
2xsin
1
lim
x4
dx
d
2xsinln
dx
d
lim
x4
2xsinln
lim
:LHRBy
4
x2
4
x
2
4
x −−π
=
−π
=
−π π
→
π
→
π
→
( ) ( )
.ateminerdetinstillisThis
0
0
08
2
2cot
4
48
4
2cot2
x48
2x2cot
lim
4
x






−
π
=











 π
−π−





 π
=
−π−π
→
( )
( ) 0
0
0
2
sinln
4
4
4
2sinln
x4
2xsinln
lim 22
4
x
=





 π
=











 π
−π











 π
=
−ππ
→
( ) 01ln
:Note
=
( ) ∞=∞ln
( ) −∞=0ln
.
[ ]
( )[ ]
( )
32
x2csc4
lim
)4(8
2x2csc2
lim
x48
dx
d
2xcot2
dx
d
lim
:LHRpeatRe
2
4
x
2
4
x
4
x
−
=
−−
−
=
−π−
π
→
π
→
π
→
( )
8
1
1
8
1
4
2csc
8
1
x2csc
8
1
lim
2
2
2
4
x
−=−=










 π
−=−⇒ π
→
( )
( ) 8
1
x4
sin2xln
lim 2
4
x
−=
−
∴
→ ππ
.
x
2
x
e
x
lim.4 +∞→
( )
∞+
∞
=
∞+
=⇒ ∞++∞→
ee
x
lim
2
x
2
x
[ ]
[ ] ( )
( )
∞+
∞+
=
∞+
=== ∞++∞→+∞→+∞→
e
2
1e
2x
lim
e
dx
d
x
dx
d
lim
e
x
lim
:LHRBy
xx
x
2
xx
2
x
[ ]
[ ]
( )
( )
0
2
e
2
1e
12
lim
e
dx
d
2x
dx
d
lim
:LHRpeatRe
xx
x
x
=
∞+
====⇒ ∞++∞→+∞→
0
e
x
lim x
2
x
=∴
+∞→
.
3xtanln
3xcosln
lim.5
6
x
π
→
( )
( ) ∞
∞
=
∞
=
π
π
=





 π





 π
=⇒ π
→
-
ln
0ln
2
tanln
2
cosln
6
3tanln
6
3cosln
3xtanln
3xcosln
lim
6
x
( ) 01ln
:Note
=
( ) ∞=∞ln
( ) −∞=0ln
[ ]
[ ]
( )
( )3x3sec
x3tan
1
3x3sin
cos3x
1
lim
3xtanln
dx
d
3xcosln
dx
d
lim
3xtanln
3xcosln
lim
:LHRApply
2
6
x
6
x
6
x
−
== π
→
π
→
π
→
x3cos
1
3xcos
x3sin
lim
x3sec
x3tan
lim
3x3sec
x3tan
1
3xtan3
lim
2
2
2
6
x
2
2
6
x26
x
π
→
π
→
π
→
−=





−=
•





−
( ) 1
6
3sinx3sinlim
2
2
6
x
−=










 π
−=⇒ π
→
1
3xtanln
3xcosln
lim
6
x
−=∴
→
π
.
( ) ( ) ( )
( )
( ) ( )
( ) ( )
( )
( )
applies.RulesHopital'L'casetheof
eitherIn.or
0
0
toresultmaywhichevaluatedislimitthethen
xg
1
xf
limxgxflim
,Henceone.equivalentantodtransforme
isproductstheirlimit,suchevaluateTolimit.itsapproaches
xas0or0formthehavingundefinedisxgandxf
ofproducttheunsigned),orsignedbecould(which0xglimand
0xflimthatsuchfunctionsabledifferentitwoarexgandxfIf.A
:onDefininiti
axax
ax
ax
∞
∞
=•
•∞∞•
=
=
→→
→
→
∞∞∞• -and0FORMSATEINDETERMINThe
.
( ) ( ) ( )
( ) ( )[ ]
( ) ( )[ ] ( ) ( )
Rule.sHopital'L'applyThen.or
0
0
toresultmay
evaluatedwhenlimitwhosequotientequivalentaninto
differencethengtransformibyevaluatedbecouldlimitThe
.xglimxflimxgxflimisThat.-
formtheofateindeterminbetosaidisxgxflimthe
then,positivebotharewhichxglimand,xflimIf.B
axaxax
ax
axax
∞
∞
∞−∞=−=−⇒∞∞
−
∞=∞=
→→→
→
→→
∞∞∞• -and0FORMSATEINDETERMINThe
.
( ) ( )
( ) ( )
( ) ( )
( ) ( )
( ) ( )[ ] ( )
LHR.thenandlogarithm
ofpropertiestheapplythenfunction,theforyvariable
alettingbyevaluatedbemayformsateindeterminThese
ly.respective,1,,0formsateminerdetintheassumed
xflimexpressionthethenorapproachesxasor
xglimand,1xflim
or,0xglimand,xflim
or,0xglimand,0xflim
:ifand,xgandxffunctionstwoGiven
:Definition
00
xg
ax
axax
axax
axax
∞
→
→→
→→
→→
∞
∞−∞+
∞==•
=∞=•
==•
∞
∞ 1and,,0FORMSATEINDETERMINThe 00
.
EXAMPLE:
Evaluate the following limits:
[ ]2xcscxlim.1 0x→
[ ] [ ] ∞•==→
00csc02xcscxlim0x
[ ]
0
0
0sin
0
sin2x
x
lim2xcscxlim
:functionrationalequivalentantofunctionthegminTransfor
0x0x
=== →→
[ ]
[ ] ( )( )
[ ]
2
1
2xcscxlim
2
1
)0(cos2
1
2cos2x
1
lim
2cos2x
1
lim
sin2x
dx
d
x
dx
d
lim
sin2x
x
lim
:LHRApply
0x
0x0x0x0x
=∴⇒==
===
→
→→→→
.
[ ]xlnxlim.2 0x→
[ ] ( ) ( )∞−==→
00ln0xlnxlim0x
[ ]
∞
∞−
=== →→
0
1
0ln
x
1
xln
limxlnxlim
:functionequivalentantofunctiongiventhegminTransfor
0x0x
[ ] 0xlnxlim
0x
=∴
→
[ ] ( )
( ) 0xlim
x
1
1
x
1
lim
x
1
dx
d
xln
dx
d
lim
x
1
xln
lim
:LHRApply
0x
2
0x0x0x
=−=
−
=




= →→→→
.




−
−→
1x
1
xln
1
lim.3 1x
∞−∞=−=
−
−=



−
−→
0
1
0
1
11
1
1ln
1
1x
1
xln
1
lim1x
( )
( )
( )
( ) 0
0
1ln1-1
1ln11
xln1-x
xln1x
lim
1x
1
xln
1
lim
:fractionsimpleaotgminTransfor
1x1x
=
−−
=
−−
=



−
− →→
( )[ ]
( )[ ]
( )
( ) ( ) ( )( )1xln1
x
1
1x
1
x
1
1
lim
xln1-x
dx
d
xln1x
dx
d
lim
1x
1
xln
1
lim
:LHRApply
1x1x1x
+





−




−
=
−−
=



−
− →→→
( ) ( ) 0
0
1ln111
11
xlnx1-x
1x
lim
x
xlnx1-x
x
1-x
lim 1x1x
=
+−
−
=
+
−
=
+
⇒ →→
.
( ) [ ]
[ ] ( ) ( )( )1xln1
x
1
x1
1
lim
xlnx1-x
dx
d
1-x
dx
d
lim
xlnx1-x
1-x
lim
:LHRagainApply
1x1x1x
++
=
+
=
+
⇒ →→→
( ) 2
1
1ln2
1
xln2
1
lim1x
=
+
=
+
⇒ →
2
1
1x
1
xln
1
lim
1x
=



−
−∴
→
.




−→
x2secx
1
x
1
lim.4 220x
( )
∞∞=−=−=



−→
-
0
1
0
1
0sec0
1
0
1
x2secx
1
x
1
lim 220x
( )
0
0
0
02cos1
x
cos2x-1
lim
x
x2cos
x
1
lim
x2secx
1
x
1
lim
:functionequivalentthetogminTransfor
20x220x220x
=
−
=



=



−=



− →→→
[ ]
[ ]
( )( ) ( )
0
0
0
02sin
x2
2x2sin
lim
x
dx
d
cos2x-1
dx
d
lim
x
cos2x-1
lim
:LHRApply
0x
2
0x20x
==
−−
==



→→→
( ) ( )
( )
( )( )( )
20cos2x2cos2lim
1
12x2cos
lim
x
dx
d
x2sin
dx
d
lim
x
x2sin
lim
:againLHRApply
0x0x0x0x
===== →→→→
2
x2secx
1
x
1
lim 220x
=





−∴
→
.
[ ]x
0x
x2lim.5 →
[ ] ( )[ ] 00x
0x
002x2lim ==→
[ ]x
x2yLet =
[ ]
[ ]
x
1
x2ln
2xlnxyln
x2lnyln
x
==
=
( )
∞
∞−
=
∞
=== →→
0ln
0
1
02ln
x
1
x2ln
limylnlim
:sidesbothonitlimtheApply
0x0x
[ ] ( )
( ) 0xlim
x
1
2
x2
1
x
1
dx
d
x2ln
dx
d
lim
x
1
x2ln
lim
:LHRApply
0x
2
0x0x
=−=
−
=




= →→→
( )
( ) 12xlimthereforethen
2xysince
1ylimeylim
:sidesbothoffunctioninversetheTake
x
0x
x
0x
0
0x
=
=
=→=
→
→→
0ylnlim
0
x
1
x2ln
limylnlim
0x
0x0x
=
==
→
→→
.
( ) 1x
1
1x
xlim.6 −
→ +
( ) ( ) ( ) ( )∞
−−
→
===+
111xlim 0
1
11
1
1x
1
1x
( ) 1x
1
xyLet −=
( ) ( )
1x
xln
xln
1x
1
xlnyln 1x
1
−
=
−
== −
0
0
11
1ln
1x
xln
limylnlim
:1xassidesbothonitlimtheApplying
1x1x
=
−
=
−
=
→
++
→→
+
( )
( )
( )
1
1
x
1
lim
1
1
x
1
lim
1x
dx
d
xln
dx
d
lim
1x
xln
lim
:memberrighttheonLHRApply
1x1x1x1x
===
−
=
− ++++
→→→→
.
( )
( ) 72.2exlim
xybuteylim
:sidesbothoffunctioninversethetake,1ylnlim
1x
xln
lim
,Thus
1x
1
1x
1x
1
1
1x
1x1x
==∴
==
==
−
−
→
−
→
→→
+
+
++
( )x
0x
xcotlim.7 +
→
( ) ( ) 00x
0x
0cotxcotlim ∞==+
→
( )
( )
x
1
xcotln
xcotlnxxcotlnyln
xcotyLet
x
x
===
=
( ) ( )
∞
∞
=
∞
∞
=
=
+
++
→
→→
ln
0
1
0cotln
lim
x
1
xcotln
limylnlim
:sidesbothonlimitthepplyA
0x
0x0x
( ) ( )( )
2
2
0x0x0x
x
1
1xcsc
xcot
1
lim
x
1
dx
d
xcotln
dx
d
lim
x
1
xcotln
lim
:memberrightonLHRApply
−
−
=






= +++
→→→
xcosxsin2
x2
lim
x
1
xcosxsin
1
lim
x
1
xsin
1
xcos
xsin
lim
2
0x
2
0x
2
2
0x ⋅
⋅
==






= +++
→→→
( )
( ) 0
0
0sin
02
x2sin
x2
lim
22
0x
=== +
→
( )
( ) ( )( ) x2cos
x2
lim
2x2cos
x4
lim
x2sin
dx
d
x2
dx
d
lim
x2sin
x2
lim
:againLHRApply
0x0x
2
0x
2
0x ++++
→→→→
===
( )
( )
0
1
0
0cos
02
===
( ) ( ) 1xcotlimthenxcotySince
1eylim
sidesbothoffunctioninversethetake,0ylnlim
x
1
xcotln
lim
,Hence
x
0x
x
0
0x
0x0x
=∴=
==
==
+
+
++
→
→
→→
x4sin
xtanx2
lim.1
0x
+
→






−
→ 220y y
1
ysin
1
lim.2
xsin
x2
lim.3 10x −→






→ ycosln
y
lim.4
2
0y
( )
x3
x2ln
lim.5
3
x +∞→
( ) 





−
+ −→ x2tan
1
x1ln
1
lim.8 10x
( )x
4
2
0x
x1lim.9 +
→






+∞→ x2
2
x e
x3
lim.10
( ) 2
x
2
2
0x
xsin1lim.11 +
→
( )x
2
x
0x
x3elim.12 +
→
x2tanln
x2cosln
lim.13
4
x
π
→( )x
1
0x
x2sinx2coslim.6 −
→
( )( )xcscxsinlim.15 1
0x
−
→
x
x
2
0x
e1lim.7 







++
→
( ) xlnxcoslim.14 1
0x
−
→ +
EXERCISES: Evaluate the following limits.

L16 indeterminate forms (l'hopital's rule)

  • 1.
  • 2.
    OBJECTIVES: • define, determine,enumerate the different indeterminate forms of functions; • apply the theorems on differentiation in evaluating limits of indeterminate forms of functions using L’Hopital’s Rule.
  • 3.
    . ( )( ) () 2313-xlim 1x 3x1-x lim 1x 3x4x lim :followsasnumeratorthefactorweexist,tolimit theforandform,ateindeterminanislimitthe 0 0 11 3)1(4)1( 1x 3x4x lim 1x 3x4x limofitlimtheEvaluate:callRe 1x1x 2 1x 22 1x 2 1x −=−== − − = − +− = − +− = − +− − +− →→→ → → 2 1x 3x4x lim,thus 2 1x −= − +− → used.bewillRulesHopital'L'onTheoremslimit saidtheevaluateToexample.secondthetoappliedbelonger nocanproblemsprevioustheinappliedprincipletheObviously, 0 0 0 )0sin( )0(2 )0(2sin 2x 2xsin lim 2x 2xsin limtheevaluatingconsiderusLet 0x 0x ===→ →
  • 4.
  • 5.
    . Theorem 3.6.1 (p.220) L'Hôpital's Rule for Form 0/0
  • 6.
  • 7.
    Theorem 3.6.2 (p.222) L'Hopital's Rule for Form ∞/∞
  • 8.
    . 2x 2xsin lim.1 0x→ EXAMPLE: Evaluate thefollowing limits. ( ) ( ) ( ) 0 0 0 0sin 02 02sin 2x 2xsin lim0x ===→ ( ) ( ) ( ) ( ) ( ) 10cos 2 02cos2 12 2x2cos lim 2x dx d 2xsin dx d lim 2x 2xsin lim :Rules'Hopital'LgsinuBy 0x0x0x === == →→→ 1 2x 2xsin lim 0x =∴ →
  • 9.
    .3ysin-y 3y-ytan lim.2 0y→ ( )( ) ( ) ( ) 0 0 00 00 0sin3-0 03-0tan 3ysin-y 3y-ytan lim0y = − − ==→ ( ) ( ) ( ) ( ) ( ) 1 2 2 31 31 03cos-1 30sec 33ycos-1 13ysec lim 3ysin-y dx d 3y-ytan dx d lim 3ysin-y 3y-ytan lim :LHRBy 2 2 0y0y0y = − − = − − = − = − == →→→ 1 3ysin-y 3y-ytan lim 0y =∴ →
  • 10.
    . ( ) ( )2 4 xx4 2xsinln lim.3 −ππ → ( ) ( ) ( ) ( ) ( ) ( )( )4x42 2x2cos 2xsin 1 lim x4 dx d 2xsinln dx d lim x4 2xsinln lim :LHRBy 4 x2 4 x 2 4 x −−π = −π = −π π → π → π → ( ) ( ) .ateminerdetinstillisThis 0 0 08 2 2cot 4 48 4 2cot2 x48 2x2cot lim 4 x       − π =             π −π−       π = −π−π → ( ) ( ) 0 0 0 2 sinln 4 4 4 2sinln x4 2xsinln lim 22 4 x =       π =             π −π             π = −ππ → ( ) 01ln :Note = ( ) ∞=∞ln ( ) −∞=0ln
  • 11.
    . [ ] ( )[] ( ) 32 x2csc4 lim )4(8 2x2csc2 lim x48 dx d 2xcot2 dx d lim :LHRpeatRe 2 4 x 2 4 x 4 x − = −− − = −π− π → π → π → ( ) 8 1 1 8 1 4 2csc 8 1 x2csc 8 1 lim 2 2 2 4 x −=−=            π −=−⇒ π → ( ) ( ) 8 1 x4 sin2xln lim 2 4 x −= − ∴ → ππ
  • 12.
    . x 2 x e x lim.4 +∞→ ( ) ∞+ ∞ = ∞+ =⇒∞++∞→ ee x lim 2 x 2 x [ ] [ ] ( ) ( ) ∞+ ∞+ = ∞+ === ∞++∞→+∞→+∞→ e 2 1e 2x lim e dx d x dx d lim e x lim :LHRBy xx x 2 xx 2 x [ ] [ ] ( ) ( ) 0 2 e 2 1e 12 lim e dx d 2x dx d lim :LHRpeatRe xx x x = ∞+ ====⇒ ∞++∞→+∞→ 0 e x lim x 2 x =∴ +∞→
  • 13.
    . 3xtanln 3xcosln lim.5 6 x π → ( ) ( )∞ ∞ = ∞ = π π =       π       π =⇒ π → - ln 0ln 2 tanln 2 cosln 6 3tanln 6 3cosln 3xtanln 3xcosln lim 6 x ( ) 01ln :Note = ( ) ∞=∞ln ( ) −∞=0ln [ ] [ ] ( ) ( )3x3sec x3tan 1 3x3sin cos3x 1 lim 3xtanln dx d 3xcosln dx d lim 3xtanln 3xcosln lim :LHRApply 2 6 x 6 x 6 x − == π → π → π → x3cos 1 3xcos x3sin lim x3sec x3tan lim 3x3sec x3tan 1 3xtan3 lim 2 2 2 6 x 2 2 6 x26 x π → π → π → −=      −= •      − ( ) 1 6 3sinx3sinlim 2 2 6 x −=            π −=⇒ π → 1 3xtanln 3xcosln lim 6 x −=∴ → π
  • 14.
    . ( ) () ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) applies.RulesHopital'L'casetheof eitherIn.or 0 0 toresultmaywhichevaluatedislimitthethen xg 1 xf limxgxflim ,Henceone.equivalentantodtransforme isproductstheirlimit,suchevaluateTolimit.itsapproaches xas0or0formthehavingundefinedisxgandxf ofproducttheunsigned),orsignedbecould(which0xglimand 0xflimthatsuchfunctionsabledifferentitwoarexgandxfIf.A :onDefininiti axax ax ax ∞ ∞ =• •∞∞• = = →→ → → ∞∞∞• -and0FORMSATEINDETERMINThe
  • 15.
    . ( ) () ( ) ( ) ( )[ ] ( ) ( )[ ] ( ) ( ) Rule.sHopital'L'applyThen.or 0 0 toresultmay evaluatedwhenlimitwhosequotientequivalentaninto differencethengtransformibyevaluatedbecouldlimitThe .xglimxflimxgxflimisThat.- formtheofateindeterminbetosaidisxgxflimthe then,positivebotharewhichxglimand,xflimIf.B axaxax ax axax ∞ ∞ ∞−∞=−=−⇒∞∞ − ∞=∞= →→→ → →→ ∞∞∞• -and0FORMSATEINDETERMINThe
  • 16.
    . ( ) () ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )[ ] ( ) LHR.thenandlogarithm ofpropertiestheapplythenfunction,theforyvariable alettingbyevaluatedbemayformsateindeterminThese ly.respective,1,,0formsateminerdetintheassumed xflimexpressionthethenorapproachesxasor xglimand,1xflim or,0xglimand,xflim or,0xglimand,0xflim :ifand,xgandxffunctionstwoGiven :Definition 00 xg ax axax axax axax ∞ → →→ →→ →→ ∞ ∞−∞+ ∞==• =∞=• ==• ∞ ∞ 1and,,0FORMSATEINDETERMINThe 00
  • 17.
    . EXAMPLE: Evaluate the followinglimits: [ ]2xcscxlim.1 0x→ [ ] [ ] ∞•==→ 00csc02xcscxlim0x [ ] 0 0 0sin 0 sin2x x lim2xcscxlim :functionrationalequivalentantofunctionthegminTransfor 0x0x === →→ [ ] [ ] ( )( ) [ ] 2 1 2xcscxlim 2 1 )0(cos2 1 2cos2x 1 lim 2cos2x 1 lim sin2x dx d x dx d lim sin2x x lim :LHRApply 0x 0x0x0x0x =∴⇒== === → →→→→
  • 18.
    . [ ]xlnxlim.2 0x→ [] ( ) ( )∞−==→ 00ln0xlnxlim0x [ ] ∞ ∞− === →→ 0 1 0ln x 1 xln limxlnxlim :functionequivalentantofunctiongiventhegminTransfor 0x0x [ ] 0xlnxlim 0x =∴ → [ ] ( ) ( ) 0xlim x 1 1 x 1 lim x 1 dx d xln dx d lim x 1 xln lim :LHRApply 0x 2 0x0x0x =−= − =     = →→→→
  • 19.
    .     − −→ 1x 1 xln 1 lim.3 1x ∞−∞=−= − −=    − −→ 0 1 0 1 11 1 1ln 1 1x 1 xln 1 lim1x ( ) () ( ) ( ) 0 0 1ln1-1 1ln11 xln1-x xln1x lim 1x 1 xln 1 lim :fractionsimpleaotgminTransfor 1x1x = −− = −− =    − − →→ ( )[ ] ( )[ ] ( ) ( ) ( ) ( )( )1xln1 x 1 1x 1 x 1 1 lim xln1-x dx d xln1x dx d lim 1x 1 xln 1 lim :LHRApply 1x1x1x +      −     − = −− =    − − →→→ ( ) ( ) 0 0 1ln111 11 xlnx1-x 1x lim x xlnx1-x x 1-x lim 1x1x = +− − = + − = + ⇒ →→
  • 20.
    . ( ) [] [ ] ( ) ( )( )1xln1 x 1 x1 1 lim xlnx1-x dx d 1-x dx d lim xlnx1-x 1-x lim :LHRagainApply 1x1x1x ++ = + = + ⇒ →→→ ( ) 2 1 1ln2 1 xln2 1 lim1x = + = + ⇒ → 2 1 1x 1 xln 1 lim 1x =    − −∴ →
  • 21.
    .     −→ x2secx 1 x 1 lim.4 220x ( ) ∞∞=−=−=    −→ - 0 1 0 1 0sec0 1 0 1 x2secx 1 x 1 lim220x ( ) 0 0 0 02cos1 x cos2x-1 lim x x2cos x 1 lim x2secx 1 x 1 lim :functionequivalentthetogminTransfor 20x220x220x = − =    =    −=    − →→→ [ ] [ ] ( )( ) ( ) 0 0 0 02sin x2 2x2sin lim x dx d cos2x-1 dx d lim x cos2x-1 lim :LHRApply 0x 2 0x20x == −− ==    →→→ ( ) ( ) ( ) ( )( )( ) 20cos2x2cos2lim 1 12x2cos lim x dx d x2sin dx d lim x x2sin lim :againLHRApply 0x0x0x0x ===== →→→→ 2 x2secx 1 x 1 lim 220x =      −∴ →
  • 22.
    . [ ]x 0x x2lim.5 → [] ( )[ ] 00x 0x 002x2lim ==→ [ ]x x2yLet = [ ] [ ] x 1 x2ln 2xlnxyln x2lnyln x == = ( ) ∞ ∞− = ∞ === →→ 0ln 0 1 02ln x 1 x2ln limylnlim :sidesbothonitlimtheApply 0x0x [ ] ( ) ( ) 0xlim x 1 2 x2 1 x 1 dx d x2ln dx d lim x 1 x2ln lim :LHRApply 0x 2 0x0x =−= − =     = →→→ ( ) ( ) 12xlimthereforethen 2xysince 1ylimeylim :sidesbothoffunctioninversetheTake x 0x x 0x 0 0x = = =→= → →→ 0ylnlim 0 x 1 x2ln limylnlim 0x 0x0x = == → →→
  • 23.
    . ( ) 1x 1 1x xlim.6− → + ( ) ( ) ( ) ( )∞ −− → ===+ 111xlim 0 1 11 1 1x 1 1x ( ) 1x 1 xyLet −= ( ) ( ) 1x xln xln 1x 1 xlnyln 1x 1 − = − == − 0 0 11 1ln 1x xln limylnlim :1xassidesbothonitlimtheApplying 1x1x = − = − = → ++ →→ + ( ) ( ) ( ) 1 1 x 1 lim 1 1 x 1 lim 1x dx d xln dx d lim 1x xln lim :memberrighttheonLHRApply 1x1x1x1x === − = − ++++ →→→→
  • 24.
    . ( ) ( )72.2exlim xybuteylim :sidesbothoffunctioninversethetake,1ylnlim 1x xln lim ,Thus 1x 1 1x 1x 1 1 1x 1x1x ==∴ == == − − → − → →→ + + ++ ( )x 0x xcotlim.7 + → ( ) ( ) 00x 0x 0cotxcotlim ∞==+ → ( ) ( ) x 1 xcotln xcotlnxxcotlnyln xcotyLet x x === =
  • 25.
    ( ) () ∞ ∞ = ∞ ∞ = = + ++ → →→ ln 0 1 0cotln lim x 1 xcotln limylnlim :sidesbothonlimitthepplyA 0x 0x0x ( ) ( )( ) 2 2 0x0x0x x 1 1xcsc xcot 1 lim x 1 dx d xcotln dx d lim x 1 xcotln lim :memberrightonLHRApply − − =       = +++ →→→ xcosxsin2 x2 lim x 1 xcosxsin 1 lim x 1 xsin 1 xcos xsin lim 2 0x 2 0x 2 2 0x ⋅ ⋅ ==       = +++ →→→ ( ) ( ) 0 0 0sin 02 x2sin x2 lim 22 0x === + →
  • 26.
    ( ) ( )( )( ) x2cos x2 lim 2x2cos x4 lim x2sin dx d x2 dx d lim x2sin x2 lim :againLHRApply 0x0x 2 0x 2 0x ++++ →→→→ === ( ) ( ) 0 1 0 0cos 02 === ( ) ( ) 1xcotlimthenxcotySince 1eylim sidesbothoffunctioninversethetake,0ylnlim x 1 xcotln lim ,Hence x 0x x 0 0x 0x0x =∴= == == + + ++ → → →→
  • 27.
    x4sin xtanx2 lim.1 0x + →       − → 220y y 1 ysin 1 lim.2 xsin x2 lim.310x −→       → ycosln y lim.4 2 0y ( ) x3 x2ln lim.5 3 x +∞→ ( )       − + −→ x2tan 1 x1ln 1 lim.8 10x ( )x 4 2 0x x1lim.9 + →       +∞→ x2 2 x e x3 lim.10 ( ) 2 x 2 2 0x xsin1lim.11 + → ( )x 2 x 0x x3elim.12 + → x2tanln x2cosln lim.13 4 x π →( )x 1 0x x2sinx2coslim.6 − → ( )( )xcscxsinlim.15 1 0x − → x x 2 0x e1lim.7         ++ → ( ) xlnxcoslim.14 1 0x − → + EXERCISES: Evaluate the following limits.