demostraciones de derivadas por medio de limites
DESCRIPTION
Este documento, es una guía para el estudiante que dese saber como obtener las formulas de las derivadas usuales. Mediante un lenguaje formal se demuestran una a una las derivadas, empleando la definición formal.TRANSCRIPT
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
Demuestre empleando la definición formal de derivada, cada una de las siguientes expresiones:
D V N Ing. ELECTICA POTENCIA Página 1
13 .)[ sen ( x ) ]'=cos ( x ) .14 . )[cos ( x ) ] '=−sen (x ).15 .)[ tg ( x ) ]'=sec2( x ).16 .) [ctg( x ) ] '=−csc2( x ) .17 .) [sec ( x ) ]'=sec ( x )⋅tg ( x ) .18 .)[ csc ( x ) ]'=−csc ( x )⋅ctg( x ).
19 .)[ arcsen( x ) ] '=1
√1−x2.
(−1<x<1) .
20 .)[ arccos( x ) ] '=−1
√1−x2.
(−1<x<1) .
21 .)[ arctg( x )] '=11+x2
.
22 .)[ arcctg (x )] '=−11+x2
.
23 .)[ arc sec ( x ) ] '=1|x|⋅√ x2−1
,(1<|x|) .
24 . )[ arc csc( x )] '=−1|x|⋅√x2−1
,(1<|x|).
1. )(x )'=1 .2. )(k ) '=0 .3. )( xn) '=nxn−1.4 . )(ax) '=ax ln( a) .5. )(ex )'=e x .
6 .)[ ln( x ) ] '=1x,( x>0 ).
7 .)[ loga ( x ) ]'=1x ln(a )
≡loga (e )x
.
( x>0 )∧(a>0 )8 .)[ f ( x )±g ( x ) ]'=f '( x )±g ' ( x ).9 .)[ f ( x )⋅g (x )] '=f ' ( x )⋅g( x )+ f ( x )⋅g ' ( x ).
10. )[ f ( x )g ( x ) ]'
=f '( x )⋅g ( x )−f ( x )⋅g '( x )
[g (x )]2g ( x )≠0 .
11. )[ k⋅f ( x ) ]'=k⋅f ' ( x )
12. )[kf ( x ) ]'
=−k
[ f (x )]2, f ( x )≠0 .
2 .) f ( x )=k⇒ k≡x0k∴ f ( x )= x0 kf ( x+h )=( x+h )0 k
( k ) '=limh→0
( x+h )0k−x0kh
≡k limh→0
( x+h )0−x0
h
( k ) '=k limh→0
x+hx+h
−xx
h≡k lim
h→0
x (x+h )−x ( x+h )x ( x+h)h
( k ) '=k limh→0
x ( x+h ) (1−1 )x (x+h )h
( k ) '=k limh→0
(1−1 )+(eh−eh )h
( k ) '=k limh→0
(eh−1 )−(eh−1 )h
( k ) '=k [ limh→0 (eh−1 )h
−limh→0
(eh−1 )h ]
( k ) '=k (1−1 ) ∴( k ) '=0R // .
1 .) f ( x )=x
[ f ( x ) ] '=limh→0
f ( x+h )−f ( x )h
.
( x )'=limh→ 0
( x+h )−xh
( x )'=limh→ 0
x+h−xh
( x )'=limh→ 0
hh=1 .R //
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 2
3 .) f (x )=xn
( xn ) '= limx→0
( x+h )n−xn
h
( xn ) '= limh→0
(n0 )xn+(n1 ) xn−1h+(n2 ) xn−2 h2+…+(nn−2) x2hn−2+(nn−1)xhn−1+(nn )hn−xn
h
( xn ) '= limh→0
xn+nxn−1h+n(n−1)2
xn−2 h2+…+n (n−1 )2
x2hn−2+nxhn−1+hn−xn
h
( xn ) '= limh→0
nxn−1h+n(n−1)2
xn−2h2+…+n(n−1)2
x2hn−2+nxhn−1+hn
h
( xn ) '= limh→0
h[nxn−1+n(n−1)2xn−2h+…+
n(n−1)2
x2hn−3+nxhn− 2+hn−1]h
( xn ) '= limh→0 [nxn−1+n(n−1)2
xn−2 h+…+n(n−1)2
x2hn−3+nxhn−2+hn−1]( xn ) '=nxn−1+
n(n−1)2
xn−2( 0)+…+n (n−1 )2
x2 (0)+nx (0 )+(0 )
( xn ) '=nxn−1R // .
( ax) '=ax ln (a ) limt→0
(1t )(1t )
⋅tln ( t+1 )
( ax) '=ax ln (a ) limt→0
11tln ( t+1)
( ax) '=ax ln (a ) limt→0
1
ln ( t+1)1t
( ax) '=ax ln (a )1
limt→0ln ( t+1)
1t
limt→0ln ( t+1 )
1t ≡ln [ lim
t→0( t+1)
1t ]=ln (e )
( ax) '=ax ln (a )R // .
4 . ) f ( x )=ax
(ax )'=limh→0
ax+h−ax
h.
(ax )'=limh→0
ax (ah−1 )h
(ax )'=ax limh→0
ah−1h
t=ah−1⇒h=ln( t+1)ln( a)
(ax )'=ax limt→ 0
tln( t+1 )ln(a )
(ax )'=ax limt→ 0
ln(a )tln( t+1 )
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 3
5 .) f (x )=ex
( ex )'=limh→0
ex+h−ex
h.
( ex )'=limh→0
ex (eh−1 )h
( ex )'=ex limh→0
eh−1h
t=eh−1⇒h=ln( t+1)ln(e )
( ex )'=ex limt→0
tln( t+1 )
( ex )'=ex limt→0
11tln ( t+1 )
( ex )'=ex1
limt→0ln( t+1 )
1t
limt→0ln( t+1 )
1t ≡ln [ lim
t→0( t+1)
1t ]=ln (e )
( ex )'=ex R // .
6 .) f ( x )=ln( x )
[ ln (x )] '=limh→0
ln (x+h )−ln( x )h
[ ln (x )] '=limh→0
ln (x+hx )h
[ ln (x )] '=limh→0
1hln(1+hx )
[ ln (x )] '=limh→0
hx⋅1h⋅[ xh ln(1+hx )]
[ ln (x )] '=limh→0
1x⋅[ ln(1+hx )
xh ]
[ ln (x )] '=1xlimh→0 [ ln(1+hx )
xh ]
limh→0 [ ln(1+hx )
xh ]≡ln [ limh→0(1+hx )
xh ]=ln(e )
[ ln (x )] '=1xR // .
7 .) f ( x )=loga( x )
[ log a( x ) ] '=limh→0
loga ( x+h)−loga ( x )h
[ log a( x ) ] '=limh→0
loga (x+hx )h
[ log a( x ) ] '=limh→0
1hlog a(1+hx )
[ log a( x ) ] '=limh→0
hx⋅1h⋅[ xh loga (1+hx )]
[ log a( x ) ] '=1x⋅limh→0 [ loga(1+hx )
xh ]
limh→0 [ loga (1+hx )
xh ]≡log a[ limh→0 (1+hx )
xh ]=loga (e )
loga(e )≡ln (e )ln ( a)
∴[ loga( x )] '=1x ln (a )
R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 4
8 .) Sean f ( x ) yg( x )diferenciables enun Intervalo I .Hallar : [ f ( x )+g( x ) ] ' y [ f ( x )−g ( x ) ]'
[ f ( x )+g( x ) ] '=limh→0
[ f ( x+h )+g (x+h )]−[ f ( x )+g( x )]h
[ f ( x )+g( x ) ] '=limh→0
[ f ( x+h )−f (x )]+ [g (x+h )−g (x )]h
[ f ( x )+g( x ) ] '=limh→0 [ f ( x+h )−f ( x )
h+g( x+h )−g( x )h ]
[ f ( x )+g( x ) ] '=limh→0
f ( x+h )−f (x )h
+limh→0
g( x+h)−g( x )h
[ f ( x )+g( x ) ] '=[ f ( x ) ] '+[ g( x ) ] ' R // .
[ f ( x )−g( x ) ] '=limh→0
[ f ( x+h )−g( x+h )]−[ f ( x )−g( x ) ]h
[ f ( x )−g( x ) ] '=limh→0
[ f ( x+h )−f ( x )]−[ g( x+h )−g( x ) ]h
[ f ( x )−g( x ) ] '=limh→0 [ f ( x+h)−f ( x )
h−g( x+h)−g( x )h ]
[ f ( x )−g( x ) ] '=limh→0
f (x+h )−f ( x )h
−limh→0
g ( x+h)−g ( x )h
[ f ( x )−g( x ) ] '=[ f ( x )] '−[ g( x ) ] ' R // .
9 .) Sean f ( x ) yg( x )diferenciables enun Intervalo I .Hallar : [ f ( x )⋅g( x ) ] '
[ f ( x )⋅g( x ) ] '=limh→0
[ f ( x+h )⋅g( x+h) ]−[ f ( x )⋅g ( x )]h
[ f ( x )⋅g( x ) ] '=limh→0
[ f ( x+h )⋅g( x+h) ]−[ f ( x )⋅g ( x )]+ [ f ( x )⋅g ( x+h)−f ( x )⋅g (x+h )]h
[ f ( x )⋅g( x ) ] '=limh→0
[ f ( x+h )⋅g( x+h)−f ( x )⋅g ( x+h) ]+[ f ( x )⋅g( x+h )−f ( x )⋅g( x )]h
[ f ( x )⋅g( x ) ] '=limh→0
g ( x+h)⋅[ f ( x+h)−f ( x )]+ f ( x )⋅[g( x+h )−g( x )]h
[ f ( x )⋅g( x ) ] '=limh→0 [ g( x+h)⋅f ( x+h )−f ( x )
h+ f ( x )⋅
g( x+h )−g( x )h ]
[ f ( x )⋅g( x ) ] '=limh→0
g ( x+h)⋅limh→ 0
f ( x+h )−f (x )h
+limh→0
f ( x )⋅limh→0
g ( x+h)−g ( x )h
[ f ( x )⋅g( x ) ] '=g ( x+0)⋅[ f ( x ) ] '+ f ( x )[ g (x )] '[ f ( x )⋅g( x ) ] '=g ( x )⋅[ f ( x ) ]'+f ( x )[ g( x ) ] ' R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 5
10 . )Sean f ( x ) yg (x )diferenciables enun Intervalo I .
Hallar :[ f (x )g( x ) ]'
[ f ( x )g ( x ) ]
'
=limh→0
f ( x+h )g ( x+h)
−f ( x )g ( x )
h
[ f ( x )g ( x ) ]
'
=limh→0
f ( x+h )⋅g( x )−f ( x )⋅g (x+h )h⋅[ g( x+h )⋅g( x )]
[ f ( x )g ( x ) ]
'
=limh→0
[ f ( x+h )⋅g( x )−f ( x )⋅g (x+h )]+[ f (x )⋅g ( x )−f ( x )⋅g( x )]h⋅[ g( x+h )⋅g( x )]
[ f ( x )g ( x ) ]
'
=limh→0
[ f ( x+h )⋅g( x )−f ( x )⋅g (x )]−[ f (x )⋅g( x+h)−f ( x )⋅g ( x )]h⋅[ g( x+h )⋅g( x )]
[ f ( x )g ( x ) ]
'
=limh→0
g ( x )⋅[ f ( x+h)−f ( x )]−f ( x )⋅[g (x+h )−g( x )]h⋅[ g( x+h )⋅g( x )]
[ f ( x )g ( x ) ]
'
=limh→0 [ g( x )g( x+h )⋅g ( x )
⋅f ( x+h)−f ( x )h
−f ( x )g( x+h )⋅g ( x )
⋅g( x+h )−g( x )h ]
[ f ( x )g ( x ) ]
'
=limh→0
g ( x )g ( x+h)⋅g (x )
⋅limh→0
f ( x+h)−f ( x )h
+ limh→ 0
f ( x )g (x+h )⋅g( x )
⋅limh→0
g ( x+h)−g ( x )h
[ f ( x )g ( x ) ]
'
=g ( x )g ( x+0)⋅g (x )
⋅[ f (x )] '−f ( x )g( x+0 )⋅g( x )
⋅[ g( x )] '
[ f ( x )g ( x ) ]
'
=g ( x )⋅[ f ( x ) ]'g ( x )⋅g( x )
−f ( x )⋅[ g( x )] 'g( x )⋅g ( x )
≡g( x )⋅[ f ( x ) ] '−f ( x )⋅[ g (x )] '
[ g( x )]2R // , g( x )≠0
11. )Sea g( x )diferenciable enun Intervalo I .
Hallar :[kg( x ) ]' , k∈ℜ .
[kg ( x ) ]'
=limh→0
kg ( x+h)
−kg ( x )
h≡[kg( x ) ]
'
=limh→0
k⋅g ( x )−k⋅g( x+h)h⋅[g (x+h )⋅g( x ) ]
[kg ( x ) ]'
=limh→0
−k⋅[g( x+h )−g( x )]h⋅[ g( x+h )⋅g( x )]
≡[kg( x ) ]'
=limh→0
−kg( x+h )⋅g( x )
⋅limh→0
g (x+h )−g (x )h
[kg ( x ) ]'
=−kg ( x+0)⋅g (x )
⋅[ g( x ) ] '≡[kg ( x ) ]'
=−k⋅[ g (x )] '[ g( x ) ]2
R // , g( x )≠0 .
12 .) Sea f ( x )diferenciable enun Intervalo I .Hallar :[ k⋅f ( x ) ] ',k∈ℜ .
[ k⋅f ( x ) ]'=limh→0
k⋅f (x+h )−k⋅f ( x )h
[ k⋅f ( x ) ]'=limh→0
k⋅[ f (x+h )−f ( x )]h
[ k⋅f ( x ) ]'=k⋅limh→0
f (x+h )−f ( x )h
[ k⋅f ( x ) ]'=k⋅[ f (x )] ' R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
Derivadas de funciones trigonométricas y sus inversas.
D V N Ing. ELECTICA POTENCIA Página 6
13 . )Sea f ( x )=sen ( x )Hallar [ f ( x )] ' .
[ sen (x )] '=limh→0
sen( x+h )−sen ( x )h
[ sen (x )] '=limh→0
sen( x )cos (h)+sen(h )cos( x )−sen ( x )h
[ sen (x )] '=limh→0
sen(h )cos ( x )h
+ limh→0
sen( x )cos (h )−sen ( x )h
[ sen (x )] '=cos ( x )⋅limh→0
sen(h )h
+limh→0
sen ( x )⋅[cos (h )−1 ]h
[ sen (x )] '=cos ( x )⋅(1 )+ limh→0
sen ( x )⋅[cos (h)−1 ]h
⋅[cos (h)+1 ][cos (h)+1 ]
[ sen (x )] '=cos ( x )+limh→0
[cos2(h )−1 ]h
⋅sen (x )cos(h )+1
[ sen (x )] '=cos ( x )−limh→0
sen2( h)h
⋅limh→ 0
sen (x )cos(h )+1
[ sen (x )] '=cos ( x )−limh→0
sen(h )h
⋅limh→ 0
sen(h )sen ( x )cos (h )+1
[ sen (x )] '=cos ( x )−(1 )⋅sen(0 )sen (x )cos (0 )+1
[ sen (x )] '=cos ( x )−(0)⋅sen (x )1+1
[ sen (x )] '=cos ( x )−02
[ sen (x )] '=cos ( x )R // .
14 .)Sea f ( x )=cos ( x )Hallar [ f ( x )] ' .
[ cos( x ) ] '=limh→0
cos( x+h )−cos ( x )h
[ cos( x ) ] '=limh→0
cos( x )cos (h )−sen (h )sen( x )−cos (x )h
[ cos( x ) ] '=limh→0
cos( x )cos (h )−cos ( x )h
−limh→0
sen(h )sen ( x )h
[ cos( x ) ] '=limh→0
cos( x )⋅[cos(h )−1 ]h
−sen ( x )⋅limh→0
sen(h )h
[ cos( x ) ] '=limh→0
cos( x )⋅[cos(h )−1 ]h
⋅[cos(h )+1 ][cos(h )+1 ]
−sen (x )⋅(1)
[ cos( x ) ] '=limh→0
[cos2(h )−1 ]h
⋅cos ( x )cos (h )+1
−sen( x )
[ cos( x ) ] '=−sen ( x )−limh→0
sen2 (h)h
⋅limh→0
cos( x )cos(h )+1
[ cos( x ) ] '=−sen ( x )−limh→0
sen(h )h
⋅limh→0
sen( h)cos (x )cos(h )+1
[ cos( x ) ] '=−sen ( x )−(1)⋅sen(0 )cos( x )cos (0 )+1
[ cos( x ) ] '=−sen ( x )−02
[ cos( x ) ] '=−sen ( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 7
15 . )Sea f ( x )=tg ( x )Hallar [ f ( x ) ] ' .
[ tg ( x ) ] '=limh→0
tg (x+h)−tg ( x )h
[ tg ( x ) ] '=limh→0
sen ( x+h)cos (x+h )
−sen ( x )cos (x )
h
[ tg ( x ) ] '=limh→0
sen ( x+h)cos ( x )−sen( x )cos ( x+h)h⋅[cos ( x+h)⋅cos( x ) ]
;α=x+h , β=x .
sen (α−β )=sen(α )cos ( β )−sen( β )cos (α )
[ tg ( x ) ] '=limh→0
sen ( x+h−x )h⋅[cos ( x+h)⋅cos( x ) ]
[ tg ( x ) ] '=limh→0
sen (h )h
⋅limh→0
1cos (x+h )⋅cos ( x )
[ tg ( x ) ] '=(1)⋅1cos( x+0 )⋅cos ( x )
[ tg ( x ) ] '=1cos (x )⋅cos (x )
≡1cos2( x )
=sec2( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 8
15 . )Sea f ( x )=tg ( x )Hallar [ f ( x ) ] ' .
[ tg ( x ) ] '=limh→0
tg (x+h)−tg ( x )h
[ tg ( x ) ] '=limh→0
sen ( x+h)cos (x+h )
−sen ( x )cos (x )
h
[ tg ( x ) ] '=limh→0
sen ( x+h)cos ( x )−sen( x )cos ( x+h)h⋅[cos ( x+h)⋅cos( x ) ]
;α=x+h , β=x .
sen (α−β )=sen(α )cos ( β )−sen( β )cos (α )
[ tg ( x ) ] '=limh→0
sen ( x+h−x )h⋅[cos ( x+h)⋅cos( x ) ]
[ tg ( x ) ] '=limh→0
sen (h )h
⋅limh→0
1cos (x+h )⋅cos ( x )
[ tg ( x ) ] '=(1)⋅1cos( x+0 )⋅cos ( x )
[ tg ( x ) ] '=1cos (x )⋅cos (x )
≡1cos2( x )
=sec2( x )R // .
16 . )Sea f (x )=ctg( x )Hallar [ f ( x ) ]' .
[ ctg(x )] '=limh→0
ctg( x+h )−ctg( x )h
[ ctg(x )] '=limh→0
cos ( x+h)sen( x+h )
−cos ( x )sen( x )
h
[ ctg(x )] '=limh→0
sen( x )cos ( x+h)−sen (x+h )cos( x )h⋅[sen ( x+h)⋅sen( x ) ]
;α=x , β=x+h.
sen (α−β )=sen(α )cos ( β )−sen( β )cos (α )
[ ctg(x )] '=limh→0
sen( x−h−x )h⋅[sen ( x+h)⋅sen( x ) ]
[ ctg(x )] '=limh→0
−sen (h )h
⋅limh→0
1sen ( x+h )⋅sen ( x )
[ ctg(x )] '=(−1 )⋅1sen ( x+0)⋅sen( x )
[ ctg(x )] '=−1sen( x )⋅sen (x )
≡−1sen2 ( x )
=−csc2 ( x )R // .
17 . )Sea f (x )=sec( x )Hallar [ f ( x ) ] ' .
[ sec( x ) ] '=limh→0
sec( x+h)−sec( x )h
[ sec( x ) ] '=limh→0
1cos(x+h )
−1cos( x )
h
[ sec( x ) ] '=limh→0
cos(x )−cos ( x+h)h⋅[cos( x+h)⋅cos( x ) ]
[ sec( x ) ] '=limh→0
cos(x )−cos ( x )cos(h )+sen ( x )sen (h)h⋅[cos( x+h)⋅cos( x ) ]
[ sec( x ) ] '=limh→0
cos(x )⋅[1−cos (h )]h⋅[cos( x+h)⋅cos( x ) ]
+ limh→ 0
sen (x )sen( h)h⋅[cos ( x+h)⋅cos ( x )]
[ sec( x ) ] '=limh→0
cos(x )⋅[1−cos (h )]h⋅[cos( x+h)⋅cos( x ) ]
⋅[1+cos(h )][1+cos(h )]
+ limh→0
sen(h )h⋅¿
⋅limh→0
sen( x )[cos( x+h)⋅cos( x ) ]
¿
[ sec( x ) ] '=limh→0
[1−cos2(h )]h
⋅limh→ 0
cos( x )[cos(h )+1 ]⋅[cos(x+h )⋅cos ( x )]
+(1 )⋅sen ( x )cos ( x+0)⋅cos( x )
[ sec( x ) ] '=limh→0
sen2 (h )h
⋅limh→0
cos( x )[cos(h)+1 ]⋅[cos( x+h )⋅cos(x )]
+sen ( x )cos( x )⋅cos( x )
[ sec( x ) ] '=limh→0
sen (h )h
⋅limh→0
sen (h )cos ( x )[cos (h)+1 ]⋅[cos( x+h)⋅cos( x ) ]
+1cos( x )
⋅sen ( x )cos( x )
[ sec( x ) ] '=(1 )⋅sen (0)cos( x )[cos(0 )+1 ]⋅[cos ( x+0)⋅cos ( x )]
+sec( x )⋅tg( x )
[ sec( x ) ] '=02cos2 (x )
+sec ( x )⋅tg( x )
[ sec( x ) ] '=sec( x )⋅tg( x )R // .
18 . )Sea f ( x )=csc( x )Hallar [ f ( x ) ] ' .
[ sec( x ) ] '=limh→0
csc( x+h)−csc( x )h
[ csc( x ) ] '=limh→0
1sen ( x+h)
−1sen ( x )
h
[ csc( x ) ] '=limh→0
sen ( x )−sen( x+h )h⋅[ sen( x+h )⋅sen( x )]
[ csc( x ) ] '=limh→0
sen ( x )−sen( x )cos (h )−sen (h )cos( x )h⋅[ sen( x+h )⋅sen( x )]
[ csc( x ) ] '=limh→0
sen ( x )⋅[1−cos(h )]h⋅[ sen( x+h )⋅sen( x )]
−limh→0
sen (h)cos ( x )h⋅[ sen( x+h )⋅sen ( x )]
[ csc( x ) ] '=limh→0
sen ( x )⋅[1−cos(h )]h⋅[ sen( x+h )⋅sen( x )]
⋅[1+cos (h )][1+cos (h )]
−limh→0
sen(h )h⋅¿
⋅limh→ 0
cos ( x )[ sen( x+h )⋅sen ( x )]
¿
[ csc( x ) ] '=limh→0
[1−cos2( h)]h
⋅limh→ 0
sen (x )[cos(h )+1 ]⋅[sen ( x+h)⋅sen ( x )]
−(1 )⋅cos( x )sen( x+0 )⋅sen ( x )
[ csc( x ) ] '=limh→0
sen2 (h )h
⋅limh→0
sen( x )[cos(h )+1 ]⋅[sen (x+h )⋅sen( x ) ]
−cos(x )sen ( x )⋅sen( x )
[ csc( x ) ] '=limh→0
sen (h )h
⋅limh→0
sen (h )sen( x )[cos (h)+1 ]⋅[ sen( x+h )⋅sen ( x )]
−1sen ( x )
⋅cos ( x )sen( x )
[ csc( x ) ] '=(1 )⋅sen (0) sen( x )[cos(0 )+1 ]⋅[ sen( x+0 )⋅sen ( x )]
−csc( x )⋅ctg( x )
[ csc( x ) ] '=02 sen2 ( x )
−csc( x )⋅ctg( x )
[ csc( x ) ] '=−csc( x )⋅ctg( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
Si f (x) es una funcion diferenciable y f -1(x) su inversa, halle [f -1(x)]’
D V N Ing. ELECTICA POTENCIA Página 9
18 . )Sea f ( x )=csc( x )Hallar [ f ( x ) ] ' .
[ sec( x ) ] '=limh→0
csc( x+h)−csc( x )h
[ csc( x ) ] '=limh→0
1sen ( x+h)
−1sen ( x )
h
[ csc( x ) ] '=limh→0
sen ( x )−sen( x+h )h⋅[ sen( x+h )⋅sen( x )]
[ csc( x ) ] '=limh→0
sen ( x )−sen( x )cos (h )−sen (h )cos( x )h⋅[ sen( x+h )⋅sen( x )]
[ csc( x ) ] '=limh→0
sen ( x )⋅[1−cos(h )]h⋅[ sen( x+h )⋅sen( x )]
−limh→0
sen (h)cos ( x )h⋅[ sen( x+h )⋅sen ( x )]
[ csc( x ) ] '=limh→0
sen ( x )⋅[1−cos(h )]h⋅[ sen( x+h )⋅sen( x )]
⋅[1+cos (h )][1+cos (h )]
−limh→0
sen(h )h⋅¿
⋅limh→ 0
cos ( x )[ sen( x+h )⋅sen ( x )]
¿
[ csc( x ) ] '=limh→0
[1−cos2( h)]h
⋅limh→ 0
sen (x )[cos(h )+1 ]⋅[sen ( x+h)⋅sen ( x )]
−(1 )⋅cos( x )sen( x+0 )⋅sen ( x )
[ csc( x ) ] '=limh→0
sen2 (h )h
⋅limh→0
sen( x )[cos(h )+1 ]⋅[sen (x+h )⋅sen( x ) ]
−cos(x )sen ( x )⋅sen( x )
[ csc( x ) ] '=limh→0
sen (h )h
⋅limh→0
sen (h )sen( x )[cos (h)+1 ]⋅[ sen( x+h )⋅sen ( x )]
−1sen ( x )
⋅cos ( x )sen( x )
[ csc( x ) ] '=(1 )⋅sen (0) sen( x )[cos(0 )+1 ]⋅[ sen( x+0 )⋅sen ( x )]
−csc( x )⋅ctg( x )
[ csc( x ) ] '=02 sen2 ( x )
−csc( x )⋅ctg( x )
[ csc( x ) ] '=−csc( x )⋅ctg( x )R // .
19 .)Sea y=sen ( x )Hallar [ f −1 ( x ) ]' .[ y−1=arcsen (x )]≡[ sen( y )=x ]Por lo tanto( y−1 ) '=( x )' .
Dadoque( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=sen( y )∴( x ) '=cos( y )
sen( y )=cateto opuestohipotenusa
sen( y )=x1
∴ cos ( y )=√1−x2
Por lo tanto( y−1 )'=1
√1−x2R //,(−1< x<1 )
yaque sen ( y )es acot adaeneste int ervalo .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 10
20 .)Sea y=cos (x )Hallar [ f−1( x )] ' .[ y−1=arccos( x ) ]≡[cos ( y )=x ]Por lo tanto( y−1) '=( x ) ' .
Dado que( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=cos ( y )∴( x )'=−sen( y )
cos ( y )=catetoopuestohipotenusa
cos ( y )=x1
∴ sen ( y )=√1−x2
Por lo tanto( y−1 )'=−1
√1−x2R //,(−1< x<1 )
yaque cos( y )esacot ada eneste int ervalo .
21 .)Sea y=tg( x )Hallar [ f−1( x ) ] ' .[ y−1=arctg ( x )]≡ [tg ( y )=x ]Por lo tanto( y−1 ) '=( x )' .
Dado que( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=tg ( y )∴( x )'=sec2 ( y )
tg ( y )=catetoopuestocatetoadyacente
tg ( y )=x1
∴ cos( y )=1
√1+x2⇒sec ( y )=√1+x2
Por lo tanto( y−1 )'=1
1+x2R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 11
22 .)Sea y=ctg( x )Hallar [ f −1 ( x ) ]' .[ y−1=arcctg ( x )]≡ [ctg( y )=x ] Por lo tanto( y−1 )'=( x ) ' .
Dado que( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=ctg( y )∴( x ) '=−csc2( y )
ctg( y )=cateto adyacentecateto opuesto
ctg( y )=x1
∴sen ( y )=1
√1+x2⇒ csc ( y )=√1+x2
Por lo tanto( y−1 )'=−1
1+x2R // .
23 .)Sea y=sec( x )Hallar [ f −1 (x )] ' .[ y−1=arc sec( x ) ]≡[sec( y )=x ]Por lo tanto( y−1) '=( x ) ' .
Dadoque( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=sec( y )∴( x )'=sec( y )⋅tg( y )
sec( y )=hipotenusacatetoadyacente
sec( y )=x1
∴ tg( y )=√ x2−1
Por lo tanto( y−1 )'=1|x|⋅√ x2−1
R //, (1<|x|)
24 . )Sea y=csc ( x )Hallar[ f −1( x ) ] ' .[ y−1=arc csc ( x ) ]≡[csc ( y )=x ] Por lo tanto( y−1 )'=( x ) ' .
Dadoque( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=csc ( y )∴( x )'=−csc( y )⋅ctg( y )
csc ( y )=hipotenusacatetoopuesto
csc ( y )=x1
∴ ctg( y )=√x2−1
Por lo tanto( y−1 )'=−1|x|⋅√x2−1
R //, (1<|x|)
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
Demuestre formalmente las derivadas de las siguientes funciones
D V N Ing. ELECTICA POTENCIA Página 12
24 . )Sea y=csc ( x )Hallar[ f −1( x ) ] ' .[ y−1=arc csc ( x ) ]≡[csc ( y )=x ] Por lo tanto( y−1 )'=( x ) ' .
Dadoque( y−1 ) '=dydx
y ( x )'=dxdy
, entonces ( y−1) '=1
(dxdy )∴( y−1 )'=1
(x )'
x=csc ( y )∴( x )'=−csc( y )⋅ctg( y )
csc ( y )=hipotenusacatetoopuesto
csc ( y )=x1
∴ ctg( y )=√x2−1
Por lo tanto( y−1 )'=−1|x|⋅√x2−1
R //, (1<|x|)
31 .)[ arg senh( x ) ] '=1
√x2+1.
32 .)[ argcosh( x ) ]'=1
√x2−1,( x>1 ).
33 .)[ arg tgh( x ) ] '=11−x2
,(|x|<1)
34 . )[arg ctgh( x ) ]'=1
1−x2.(|x|>1 )
35 .)[ argsec h( x ) ] '=−1
x⋅√1−x2
( 0<x<1) .
36 .) [argcsc h( x ) ] '=−1|x|⋅√1+ x2
( x≠0) .
25 .)[ senh ( x ) ] '=cos( x ) .26 .) [cosh ( x ) ] '=senh ( x ).27 .) [ tgh( x ) ]'=sec2h( x ).28 .)[ ctgh( x ) ]'=−csc2 ( x ).29 .)[ sech ( x ) ]'=−sec h( x )⋅tgh( x ) .30 .)[ csc h( x ) ]'=−csc h( x )⋅ctgh( x ).
senh( x )=ex−e−x
2. cosh ( x )=e
x+e−x
2.
tgh( x )=ex−e− x
e x+e−x. ctgh( x )=ex+e− x
ex−e−x.
sec h( x )=2ex+e− x
. csch (x )=2e x−e− x
.
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 13
25 .) f (x )=senh( x )
[ senh( x ) ] '=limh→0
senh ( x+h)−senh (x )h
.
[ senh( x ) ] '=limh→0
ex+h−e−x−h
2−ex−e−x
2h
[ senh( x ) ] '=limh→0
ex+h−e−x−h−ex+e− x
2h
[ senh( x ) ] '=limh→0
(ex+h−ex )−(e−x−h−e− x )2h
[ senh( x ) ] '=limh→0
ex (eh−1 )2h
−limt→0
e−x (e−h−1 )2h
[ senh( x ) ] '=limh→0
ex
2⋅limh→0
eh−1h
−limh→0
e− x
2⋅limh→0
e−h−1h
[ senh( x ) ] '=ex
2⋅(1)−e
−x
2⋅(−1)
[ senh( x ) ] '=ex+e−x
2≡cosh ( x )R // .
26 .) f ( x )=cosh ( x )
[cosh ( x ) ] '=limh→0
cosh ( x+h)−cosh ( x )h
.
[cosh ( x ) ] '=limh→0
ex+h+e− x−h
2−e
x+e−x
2h
[cosh ( x ) ] '=limh→0
ex+h+e− x−h−ex−e− x
2h
[cosh ( x ) ] '=limh→0
(ex+h−ex )+(e− x−h−e−x )2h
[cosh ( x ) ] '=limh→0
ex (eh−1 )2h
+ limt→0
e−x (e−h−1 )2h
[cosh ( x ) ] '=limh→0
ex
2⋅limh→0
eh−1h
+ limh→0
e−x
2⋅limh→0
e−h−1h
[cosh ( x ) ] '=ex
2⋅(1)+e
−x
2⋅(−1)
[cosh ( x ) ] '=ex−e−x
2≡senh( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 14
27 .) f ( x )=tgh ( x )
[ tgh ( x ) ]'=limh→0
tgh ( x+h)−tgh( x )h
.
[ tgh ( x ) ]'=limh→0
e x+h−e− x−h
e x+h+e−x−h−e
x−e− x
e x+e−x
h
[ tgh ( x ) ]'=limh→0
(ex+h−e−x−h ) (ex+e−x )−(e x+h+e−x−h) (e x−e− x )h⋅(ex+h+e−x−h ) (ex+e−x )
[ tgh ( x ) ]'=limh→0
(e2 x+h−e−h+eh−e−2 x−h )− (e2 x+h+e−h−eh−e−2 x−h)h⋅(ex+h+e−x−h ) (ex+e−x )
[ tgh ( x ) ]'=limh→0
(e2 x+h−e2 x+h)+(e−2 x−h−e−2 x−h)+2 (eh−e−h )h⋅(ex+h+e−x−h ) (ex+e−x )
[ tgh ( x ) ]'=limh→0
2 [ (eh−1 )− (e−h−1 ) ]h⋅(ex+h+e−x−h ) (ex+e−x )
[ tgh ( x ) ]'=limh→0
2
(ex+h+e− x−h) (ex+e− x )⋅[ limh→0
(eh−1 )−(e−h−1 )h ]
[ tgh ( x ) ]'=2(ex+0+e− x−0) (ex+e− x )
⋅[ limh→0
eh−1h
−limh→0
e−h−1h ]
[ tgh ( x ) ]'=2
(ex+e− x )2⋅(1−(−1 ))=[2(ex+e− x ) ]
2
=sec h2 (x )R // .
28 .) f (x )=ctgh( x )
[ctgh( x ) ] '=limh→ 0
ctgh(x+h )−ctgh( x )h
.
[ctgh( x ) ] '=limh→ 0
ex+h+e− x−h
ex+h−e−x−h−ex+e− x
ex−e−x
h
[ctgh( x ) ] '=limh→ 0
(ex+h+e−x−h ) (ex−e−x )−(ex+h−e−x−h ) (ex+e−x )h⋅(e x+h+e−x−h) (e x+e− x )
[ctgh( x ) ] '=limh→ 0
(e2 x+h+e−h−eh−e−2 x−h)−(e2 x+h−e−h+eh−e−2 x−h )h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
(e2 x+h−e2 x+h)+(e−2 x−h−e−2 x−h )−2 (eh−e−h)h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
−2 [ (eh−1 )−(e−h−1 ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
−2(ex+h−e−x−h) (e x−e− x )
⋅[ limh→0 (eh−1 )−(e−h−1 )h ]
[ctgh( x ) ] '=−2(ex+0−e−x−0) (e x−e− x )
⋅[ limh→0 eh−1h
−limh→0
e−h−1h ]
[ctgh( x ) ] '=−2
(ex−e−x )2⋅(1−(−1 ) )
[ctgh( x ) ] '=−[2(e x−e− x ) ]2
[ctgh( x ) ] '=−csch2( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 15
28 .) f (x )=ctgh( x )
[ctgh( x ) ] '=limh→ 0
ctgh(x+h )−ctgh( x )h
.
[ctgh( x ) ] '=limh→ 0
ex+h+e− x−h
ex+h−e−x−h−ex+e− x
ex−e−x
h
[ctgh( x ) ] '=limh→ 0
(ex+h+e−x−h ) (ex−e−x )−(ex+h−e−x−h ) (ex+e−x )h⋅(e x+h+e−x−h) (e x+e− x )
[ctgh( x ) ] '=limh→ 0
(e2 x+h+e−h−eh−e−2 x−h)−(e2 x+h−e−h+eh−e−2 x−h )h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
(e2 x+h−e2 x+h)+(e−2 x−h−e−2 x−h )−2 (eh−e−h)h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
−2 [ (eh−1 )−(e−h−1 ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[ctgh( x ) ] '=limh→ 0
−2(ex+h−e−x−h) (e x−e− x )
⋅[ limh→0 (eh−1 )−(e−h−1 )h ]
[ctgh( x ) ] '=−2(ex+0−e−x−0) (e x−e− x )
⋅[ limh→0 eh−1h
−limh→0
e−h−1h ]
[ctgh( x ) ] '=−2
(ex−e−x )2⋅(1−(−1 ) )
[ctgh( x ) ] '=−[2(e x−e− x ) ]2
[ctgh( x ) ] '=−csch2( x )R // .
29 .) f (x )=sec h( x )
[sec h( x ) ] '=limh→0
sec h( x+h )−sec h( x )h
.
[sec h( x ) ] '=limh→0
2
ex+h+e− x−h−2ex+e−x
h
[sec h( x ) ] '=limh→0
2 (ex+e− x )−2 (e x+h+e−x−h)h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
2 (−ex+h+ex−e− x−h+e−x )h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2 [ (ex+h−ex )+(e−x−h−e−x ) ]h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2 [ ex (eh−1 )+e−x (e−h−1 ) ]h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2(ex+h+e− x−h ) (ex+e− x )
⋅[ limh→0 ex (eh−1 )+e−x (e−h−1 )h ]
[sec h( x ) ] '=−2(ex+0+e− x−0 ) (ex+e− x )
⋅[ex limh→0 eh−1h
+e− x limh→0
e−h−1h ]
[sec h( x ) ] '=−2(ex+e−x )2
⋅(ex−e−x )
[sec h( x ) ] '=−2(ex+e−x )
⋅(ex−e− x )(ex+e−x )
[sec h( x ) ] '=−sech( x )⋅tgh( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 16
29 .) f (x )=sec h( x )
[sec h( x ) ] '=limh→0
sec h( x+h )−sec h( x )h
.
[sec h( x ) ] '=limh→0
2
ex+h+e− x−h−2ex+e−x
h
[sec h( x ) ] '=limh→0
2 (ex+e− x )−2 (e x+h+e−x−h)h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
2 (−ex+h+ex−e− x−h+e−x )h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2 [ (ex+h−ex )+(e−x−h−e−x ) ]h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2 [ ex (eh−1 )+e−x (e−h−1 ) ]h⋅(e x+h+e−x−h) (e x+e−x )
[sec h( x ) ] '=limh→0
−2(ex+h+e− x−h ) (ex+e− x )
⋅[ limh→0 ex (eh−1 )+e−x (e−h−1 )h ]
[sec h( x ) ] '=−2(ex+0+e− x−0 ) (ex+e− x )
⋅[ex limh→0 eh−1h
+e− x limh→0
e−h−1h ]
[sec h( x ) ] '=−2(ex+e−x )2
⋅(ex−e−x )
[sec h( x ) ] '=−2(ex+e−x )
⋅(ex−e− x )(ex+e−x )
[sec h( x ) ] '=−sech( x )⋅tgh( x )R // .
30 .) f (x )=csc h( x )
[csc h( x ) ] '=limh→0
csch( x+h )−csc h( x )h
.
[csc h( x ) ] '=limh→0
2
ex+h−e−x−h−2ex−e−x
h
[csc h( x ) ] '=limh→0
2 (ex−e−x )−2 (ex+h−e−x−h)h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
2 (−ex+h+e x+e−x−h−e−x )h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2 [ (ex+h−ex )−(e− x−h−e−x ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2 [ ex (eh−1 )−e− x (e−h−1 ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2(ex+h−e−x−h) (ex−e− x )
⋅[ limh→0
ex (eh−1 )−e−x (e−h−1 )h ]
[csc h( x ) ] '=−2(ex+0−e−x−0 ) (ex−e− x )
⋅[ex limh→0 eh−1h
−e−x limh→0
e−h−1h ]
[csc h( x ) ] '=−2(ex−e−x )2
⋅(ex+e−x )
[csc h( x ) ] '=−2(ex−e−x )
⋅(ex+e− x )(ex−e−x )
[csc h( x ) ] '=−csch( x )⋅ctgh( x )R // .
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
Si f (x) es una funcion diferenciable y f -1(x) su inversa, halle [f -1(x)]’
D V N Ing. ELECTICA POTENCIA Página 17
30 .) f (x )=csc h( x )
[csc h( x ) ] '=limh→0
csch( x+h )−csc h( x )h
.
[csc h( x ) ] '=limh→0
2
ex+h−e−x−h−2ex−e−x
h
[csc h( x ) ] '=limh→0
2 (ex−e−x )−2 (ex+h−e−x−h)h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
2 (−ex+h+e x+e−x−h−e−x )h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2 [ (ex+h−ex )−(e− x−h−e−x ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2 [ ex (eh−1 )−e− x (e−h−1 ) ]h⋅(e x+h−e− x−h ) (ex−e−x )
[csc h( x ) ] '=limh→0
−2(ex+h−e−x−h) (ex−e− x )
⋅[ limh→0
ex (eh−1 )−e−x (e−h−1 )h ]
[csc h( x ) ] '=−2(ex+0−e−x−0 ) (ex−e− x )
⋅[ex limh→0 eh−1h
−e−x limh→0
e−h−1h ]
[csc h( x ) ] '=−2(ex−e−x )2
⋅(ex+e−x )
[csc h( x ) ] '=−2(ex−e−x )
⋅(ex+e− x )(ex−e−x )
[csc h( x ) ] '=−csch( x )⋅ctgh( x )R // .
31 .)Sea y=senh ( x )Hallar [ f−1 (x )] ' .
x=senh( y )
sen( y )=ey−e− y
2
x=ey−e− y
22 x=e y−e− y
e y (2 x )=e y (e y−e− y )2 xe y=e2 y−1 ; t=e y
e2 y−2xe y−1=0t2−2xt−1=0
t=2 x±√4 x2+42
t=x+√ x2+1∨t=x−√x2+1e y=x+√x2+1y−1=ln (x+√ x2+1 )
( y−1) '=1
x+√x2+1⋅(1+x√x2+1 )
( y−1) '=1x+√x2+1
⋅(x+√ x2+1√x2+1 )
( y−1) '=1
√x2+1Por lo tanto( y−1 )'=1
√ x2+1R //
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 18
32 .)Sea y=cosh ( x )Hallar [ f−1 (x )] ' .
x=cosh ( y )
cos ( y )=e y+e− y
2
x=ey+e− y
22 x=e y+e− y
e y (2 x )=e y (e y+e− y )2 xe y=e2 y+1; t=e y
e2 y−2xe y+1=0t2−2xt+1=0
t=2 x±√4 x2−42
t=x+√ x2−1∨t=x−√x2−1e y=x+√x2−1y−1=ln (x+√ x2−1 )
( y−1) '=1
x+√x2−1⋅(1+ x√x2−1 )
( y−1) '=1x+√x2−1
⋅( x+√x2−1√x2−1 )
( y−1) '=1
√x2−1Por lo tanto( y−1 )'=1
√ x2−1R //,( x>1)
33 .)Sea y=tgh( x )Hallar [ f−1( x ) ] ' .
x=tgh( y )
tg( y )=ey−e− y
e y+e− y
x=ey−e− y
e y+e− y
x (e y+e− y )=e y−e− y
xe y (e y+e− y )=e y (e y−e− y )xe2 y+ x=e2 y−1e2 y−xe 2 y=x+1e2 y (1−x )=x+1
e2 y=x+11−x
2 y−1=ln(x+11−x )y−1=1
2ln(x+11−x )
( y−1) '=12⋅(1−xx+1 )⋅1−x+1+x
(1−x )2
( y−1) '=12⋅2
(1+x ) (1−x )
Por lo tanto( y−1 )'=11−x2
R //,(|x|<1)
34 . )Sea y=ctgh( x )Hallar [ f −1( x ) ] ' .
x=ctgh( y )
ctg( y )=ey+e− y
e y−e− y
x=ey+e− y
e y−e− y
x (e y−e− y )=e y+e− y
xe y (e y−e− y )=e y (e y+e− y )xe2 y−x=e2 y+1xe2 y−e2 y=x+1e2 y ( x−1 )=x+1
e2 y=x+1x−1
DERIVADA DE UNA FUNCIÓN POR MEDIO DE LÍMITES
D V N Ing. ELECTICA POTENCIA Página 19
34 . )Sea y=ctgh( x )Hallar [ f −1( x ) ] ' .
x=ctgh( y )
ctg( y )=ey+e− y
e y−e− y
x=ey+e− y
e y−e− y
x (e y−e− y )=e y+e− y
xe y (e y−e− y )=e y (e y+e− y )xe2 y−x=e2 y+1xe2 y−e2 y=x+1e2 y ( x−1 )=x+1
e2 y=x+1x−1
2 y−1=ln(x+1x−1 )y−1=1
2ln(x+1x−1 )
( y−1) '=12⋅( x−1x+1 )⋅x−1−x−1
( x−1 )2
( y−1) '=12⋅−2
( x+1 ) (x−1 )
( y−1) '=−1x2−1
Por lo tanto( y−1)'=11−x2
R //,(|x|>1)
35 .)Sea y=sech ( x )Hallar [ f−1 (x )] ' .
x=sec h( y )
sec( y )=2e y+e− y
x=2e y+e− y
x (e y+e− y )=2xe y (e y+e− y )=2e yxe2 y+ x=2e y ; t=e y
xt2−2 t+ x=0
t=2±√4−4 x22 x
t=1+√1−x2
x∨t=
1−√1−x2
x
e y=1+√1−x2
x
y−1=ln(1+√1−x2
x )
( y−1) '=x
1+√1−x2⋅(−x2
√1−x2−1−√1−x2
x2)
( y−1) '=x
1+√1−x2⋅(−x2−√1−x2−1+x2
x2√1−x2 )( y−1) '=−x
1+√1−x2⋅(1+√1−x2
x2√1−x2 )Por lo tanto( y−1 )'=−1
x √1−x2R //,(0< x<1 )
36 .) Sea y=csc h( x )Hallar [ f −1 ( x ) ]' .
x=csc h( y )
csc ( y )=2e y−e− y
x=2e y−e− y
x (e y−e− y )=2xe y (e y−e− y )=2e yxe2 y−x=2e y ; t=e y
xt2−2 t−x=0
t=2±√4+4 x22 x
t=1+√1+x2x
∨t=1−√1+ x2x
e y=1+√1+x2x
y−1=ln(1+√1+x2x )
( y−1) '=x
1+√1+x2⋅(x
2
√1+x2−1−√1+x2
x2)
( y−1) '=x
1+√1+x2⋅(x2−√1+x2−1−x2
x2 √1+x2 )( y−1) '=−x
1+√1+x2⋅(1+√1+x2x2 √1+x2 )
Por lo tanto( y−1 )'=−1|x|⋅√1+x2
R //,( x≠0 )