A Note on the Generalization of the Mean Value Theorem

International Journal of Trend in Scientific Research and Development (IJTSRD)
Volume 5 Issue 1, November-December
@ IJTSRD | Unique Paper ID – IJTSRD38258
A Note on the Generalization
Professor, Department of Electrical Engineering, I
ABSTRACT
In this paper, a new generalization of the mean value theorem
established. Based on the Rolle’s theorem, a simple proof is provided to
guarantee the correctness of such a generalization. Some corollaries are
evidently obtained by the main result. It will be shown that the mean value
theorem, the Cauchy’s mean value theorem, and the mean value theorem
for integrals are the special cases of such a generalized form. We can
simultaneously obtain the upper and lower bounds of certain integral
formulas and verify inequalities by using the main theorems. Finally,
examples are offered to illustrate the feasibility and effectiveness of the
obtained results.
KEYWORDS: Rolle’s theorem, Mean value theorem, Cauchy’s mean value
theorem, Mean value theorem for integrals, Generalized mean value theorem
1. INTRODUCTION
In the past three decades, several kinds of mean valued
theorems have been intensively investigated and
proposed, such as mean value theorem (or the theorem of
mean) [1], Cauchy’s mean value theorem (or Cauchy’s
generalized theorem of mean) [2], mean value theorem for
integrals [3], and others [3-10]. These theorems have
many theoretical and practical applications including, but
not limited to, maxima and minima, limits, inequalities,
and definite integrals. Such theorems lead to very efficient
methods for solving various problems and the importance
of such theorems lie elsewhere [1-10]. It is worth
mentioning that the proof of L’Hôpital’s rule is based on
Cauchy’s mean value theorem.
In this paper, a simple generalized form of the mean value
theorem will be investigated and established. It can be
proven that the mean value theorem, the Cauchy’s mean
value theorem, and the mean value theorem for integrals
are the special cases of such a generalized form. Based on
such a generalized form, several kinds of generalized
mean value theorems can be straightforwardly obtained. It
will be shown that the main results can be applied to
obtain the bounds of integrals. Meanwhile, we can prove
inequalities by the main theorem.
2. PROBLEM FORMULATION AND MAIN RESULTS
Now we present the main result for the generalized form
of the mean value theorem as follows.
Theorem 1. If n
f
f
f ,
,
, 2
1 L are continuous on the closed
interval [ ]
b
a, and differentiable on the open interval
( )
b
a, , then there is a point η in ( )
b
a, such that
December 2020 Available Online: www.ijtsrd.com
38258 | Volume – 5 | Issue – 1 | November-
he Generalization of the Mean Value Theorem
Yeong-Jeu Sun
f Electrical Engineering, I-Shou University, Kaohsiung, Taiwan
In this paper, a new generalization of the mean value theorem is firstly
established. Based on the Rolle’s theorem, a simple proof is provided to
guarantee the correctness of such a generalization. Some corollaries are
evidently obtained by the main result. It will be shown that the mean value
ean value theorem, and the mean value theorem
for integrals are the special cases of such a generalized form. We can
simultaneously obtain the upper and lower bounds of certain integral
formulas and verify inequalities by using the main theorems. Finally, two
examples are offered to illustrate the feasibility and effectiveness of the
theorem, Mean value theorem, Cauchy’s mean value
theorem, Mean value theorem for integrals, Generalized mean value theorem
How to cite this paper:
"A Note on the Generalization of the
Mean Value Theorem" Published in
International
Journal of Trend in
Scientific Research
and Development
(ijtsrd), ISSN: 2456
6470, Volume
Issue-1, December
2020, pp.1499
1501, URL:
www.ijtsrd.com/papers/ijtsrd38258.pdf
Copyright © 2020 by author
International Journal of Trend in
Scientific Research and Development
Journal. This is an Open Access article
distributed under
the terms of the
Creative Commons
Attribution License
(http://creativecommons.org/licenses/by/4.0)
In the past three decades, several kinds of mean valued
theorems have been intensively investigated and
proposed, such as mean value theorem (or the theorem of
mean) [1], Cauchy’s mean value theorem (or Cauchy’s
eneralized theorem of mean) [2], mean value theorem for
10]. These theorems have
many theoretical and practical applications including, but
not limited to, maxima and minima, limits, inequalities,
heorems lead to very efficient
methods for solving various problems and the importance
10]. It is worth
mentioning that the proof of L’Hôpital’s rule is based on
lized form of the mean value
theorem will be investigated and established. It can be
proven that the mean value theorem, the Cauchy’s mean
value theorem, and the mean value theorem for integrals
are the special cases of such a generalized form. Based on
ch a generalized form, several kinds of generalized
mean value theorems can be straightforwardly obtained. It
will be shown that the main results can be applied to
obtain the bounds of integrals. Meanwhile, we can prove
PROBLEM FORMULATION AND MAIN RESULTS
Now we present the main result for the generalized form
are continuous on the closed
and differentiable on the open interval
such that
( ) ( ) (
2
2
1
1
′
+
+
′
+
′ η
α
η
α
η
α n
n f
f
f L
where ( ) n
n ℜ
∈
α
α
α ,
,
, 2
1 L is any vector with
( ) ( )
[ ] 0
1
=
−
⋅
∑
=
n
i
i
i
i a
f
b
f
α .
Proof. Define
( ) ( )
∑
=
⋅
=
n
i
i
i x
f
x
T
1
: α . (2)
Obviously, the function (x
T
differentiable in ( )
b
a, . In addition, one has
( ) ( ) (a
f
b
f
b
T
n
i
i
i
n
i
i
i ⋅
=
⋅
= ∑
∑ =
= 1
1
α
α
in view of (1) and (2). Therefore, by the Rolle’s Theorem,
there exists a number η in
follows that
( ) 0
1
=
′
⋅
∑
=
n
i
i
i f η
α .
This completes our proof.
Define
( )
{ ,
,
, 2
1 ℜ
∈
ℜ
∈
= t
t
W n
n
δ
δ
δ L
with ( ) ( ) {
i
a
f
b
f i
i
i ,
: ∈
∀
−
=
δ
subspace of the Euclidean inner product space
www.ijtsrd.com e-ISSN: 2456 – 6470
-December 2020 Page 1499
he Mean Value Theorem
Shou University, Kaohsiung, Taiwan
How to cite this paper: Yeong-Jeu Sun
"A Note on the Generalization of the
Mean Value Theorem" Published in
International
Journal of Trend in
Scientific Research
and Development
(ijtsrd), ISSN: 2456-
olume-5 |
1, December
2020, pp.1499-
1501, URL:
www.ijtsrd.com/papers/ijtsrd38258.pdf
Copyright © 2020 by author (s) and
International Journal of Trend in
Scientific Research and Development
Journal. This is an Open Access article
distributed under
the terms of the
Creative Commons
Attribution License (CC BY 4.0)
http://creativecommons.org/licenses/by/4.0)
) 0
=
η ,
is any vector with
(1)
)
x is continuous in [ ]
b
a, and
. In addition, one has
) ( )
a
T
a = ,
in view of (1) and (2). Therefore, by the Rolle’s Theorem,
in ( )
b
a, such that ( ) 0
=
′ η
T . It
},
ℜ
{ }
n
,
,
2
,
1 L . Obviously, W is a
subspace of the Euclidean inner product space n
ℜ . Thus,
IJTSRD38258

International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
@ IJTSRD | Unique Paper ID – IJTSRD38258 | Volume – 5 | Issue – 1 | November-December 2020 Page 1500
by Theorem 1, we may obtain an alternative form as
follows.
Corollary 1. Let n
f
f
f ,
,
, 2
1 L are continuous in [ ]
b
a,
and differentiable in ( )
b
a, . There exists a point η on the
open interval ( )
b
a, such that
( ) ( ) ( )
( ) ,
,
,
,
,
0
2
1
2
2
1
1
⊥
∈
∀
=
′
+
+
′
+
′
W
f
f
f
n
n
n
α
α
α
η
α
η
α
η
α
L
L
where ⊥
W is the orthogonal complement of W in
( ) n
n ℜ
∈
α
α
α ,
,
, 2
1 L .
Simple setting
( ) ( ) { }
n
i
x
g
dx
x
df
i
i
,
,
2
,
1
, L
∈
∀
= in Theorem
1, we may obtain the following generalized mean value
theorem for integrals.
Corollary 2. If n
g
g
g ,
,
, 2
1 L are continuous in the
open interval ( )
b
a, , then there is a point η in ( )
b
a, such
that
( ) ( ) ( ) 0
2
2
1
1 =
+
+
+ η
α
η
α
η
α n
n g
g
g L ,
where ( ) n
n ℜ
∈
α
α
α ,
,
, 2
1 L is any vector with
( ) 0
1
=








⋅
∑ ∫
=
n
i
b
a
i
i dx
x
g
α .(3)
Based on the contra positive proposition of Theorem 1, we
may obtain the following result.
Corollary 3. Let n
f
f
f ,
,
, 2
1 L be continuous in [ ]
b
a,
and differentiable in ( )
b
a, . If there exists a vector
( ) n
n ℜ
∈
α
α
α ,
,
, 2
1 L such that
( ) ( ),
,
,
0
1
b
a
f
n
i
i
i ∈
∀
≠
′
∑
=
η
η
α (4)
then ( ) ( )
[ ] 0
1
≠
−
⋅
∑
=
n
i
i
i
i a
f
b
f
α .
Remark 1. By Theorem 1 with
( ) ( ) ( ),
,
, 1
1
2
1
2 a
f
b
f
b
a
x
x
f −
=
−
=
= α
α
0
4
3 =
=
=
= n
α
α
α L ,
in which case the condition (1) is obviously satisfied, it is
easy to see that there exists a point η in ( )
b
a, such that
( ) ( ) ( ) ( ) 0
1
1
1 =
−
+
′
− a
f
b
f
f
b
a η .
This is exactly the same as the mean value theorem.
Moreover, by Theorem 1 with
( ) ( ) ( ) ( ),
, 1
1
2
2
2
1 b
f
a
f
a
f
b
f −
=
−
= α
α
,
0
4
3 =
=
=
= n
α
α
α L
in which case the condition (1) is apparently met, it can be
shown that there exists a point η in ( )
b
a, such that
( ) ( )
[ ] ( ) ( ) ( )
[ ] ( ) 0
2
1
1
1
2
2 =
′
⋅
−
+
′
⋅
− η
η f
b
f
a
f
f
a
f
b
f .
This result is exactly the same as the Cauchy’s mean value
theorem. Besides, by Corollary 2 with
( ) ( ) ,
,
,
1 1
2
1
2 ∫
=
−
=
=
b
a
dx
x
g
b
a
x
g α
α
,
0
4
3 =
=
=
= n
α
α
α L
in which case the condition (3) is evidently satisfied, it is
easy to see that there exists a point η in ( )
b
a, such that
( ) ( ) ( ) 0
1
1 =
+
− ∫
b
a
dx
x
g
g
b
a η ,
this is exactly the same as the mean value theorem for
integrals. Consequently, we conclude that our result is a
nontrivial generalization of those results to the case with
multiple functions.
3. ILLUSTRATIVE EXAMPLES
In this section, we provide two examples to illustrate the
main results.
Example 1. Let
( ) ( ) ( ) 4
3
3
2
2
1 ,
, x
x
f
x
x
f
x
x
f =
=
= , with the open interval
( ) ( )
1
,
0
, =
b
a .
By Theorem 1, we conclude that there is a point η in ( )
1
,
0
such that
( ) ( ) ( )
( ) ( )
{ }.
0
,
,
,
,
,
0
3
2
1
3
2
1
3
2
1
3
3
2
2
1
1
=
+
+
∈
∀
=
′
+
′
+
′
α
α
α
α
α
α
α
α
α
η
α
η
α
η
α f
f
f
In case of 2
,
1 3
2
1 −
=
=
= α
α
α , we can see that
.
0
16
73
3
16
73
3
16
73
3
3
3
2
2
1
1
=







 +
′
+







 +
′
+







 +
′
f
f
f
α
α
α
Similarly, in case of 1
,
2
,
3 3
2
1 −
=
−
=
= α
α
α , we have
.
0
4
33
3
4
33
3
4
33
3
3
3
2
2
1
1
=







 +
−
′
+







 +
−
′
+







 +
−
′
f
f
f
α
α
α
Since ( )
1
,
0
16
73
3
∈
+
and ( )
1
,
0
4
33
3
∈
+
−
, Theorem 1 is
verified.

International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
@ IJTSRD | Unique Paper ID – IJTSRD38258 | Volume – 5 | Issue – 1 | November-December 2020 Page 1501
The upper and lower bounds of some integral formulas
can also be deduced by the main theorem.
Example 2. Prove that
( )
( )
2
3
2
3
2
1
≤
≤
−
∫
∫
b
a
b
a
dx
x
g
dx
x
g
if ( )
x
g1 and ( )
x
g2 are continuous in the open interval
( )
b
a, , with ( ) 0
2 >
x
g and
( )
( )
( )
b
a
x
x
x
x
g
x
g
,
,
2
cos
3
2
sin
3
2
1
∈
∀
+
= .
Proof. By Corollary 2, there exists a point η in ( )
b
a,
such that
( )
( )
( )
( )
.
4
2
sin
2
3
2
cos
3
2
sin
3
2
1
2
1






+
=
+
=
=
∫
∫
π
η
η
η
η
η
g
g
dx
x
g
dx
x
g
b
a
b
a
It follows that
( )
( )
.
2
3
2
3
2
1
≤
≤
−
∫
∫
b
a
b
a
dx
x
g
dx
x
g
This completes our proof.
4. CONCLUSION
In this paper, a new generalization of the mean value
theorem has been firstly proposed. Based on the Rolle’s
theorem, a simple proof has been provided to guarantee
the correctness of such a generalization. Some corollaries
have been evidently obtained by the main result. It has
been shown that the mean value theorem, the Cauchy’s
generalized theorem of the mean, and the mean value
theorem for integrals are the special cases of such a
generalized form. Besides, we can simultaneously obtain
the upper and lower bounds of certain integral formulas
and verify inequalities by using the main theorems.
Finally, two examples have been given to show the
feasibility and effectiveness of the obtained results.
ACKNOWLEDGEMENT
The author thanks the Ministry of Science and Technology
of Republic of China for supporting this work under grant
MOST 109-2221-E-214-014. Besides, the author is grateful
to Chair Professor Jer-Guang Hsieh for the useful
comments.
REFERENCES
[1] R. Larson and B.H. Edwards, Calculus, 11th ed.,
Australia: Cengage Learning, 2018.
[2] L.C. German, “Some variants of Cauchy's mean value
theorem,” International Journal of Mathematical
Education in Science and Technology, vol. 51, pp.
1155-1163, 2020.
[3] R.C. Wrede and M.R. Spiegel, Advanced Calculus, 3th
ed., New York: McGraw-Hill, 2010.
[4] R.S. Steiner, “Effective Vinogradov's mean value
theorem via efficient boxing,” Journal of Number
Theory, vol. 17, pp. 354-404, 2019.
[5] N. Gasmia, M. Boutayeba, A. Thabetb, and M. Aounb,
“Observer-based stabilization of nonlinear discrete-
time systems using sliding window of delayed
measurements,” Stability, Control and Application
of Time-delay Systems, pp. 367-386, 2019.
[6] N. Gasmia, M. Boutayeba, A. Thabetb, and M. Aounb,
“Nonlinear filtering design for discrete-time
systems using sliding window of delayed
measurements,” Stability, Control and Application
of Time-delay Systems, pp. 423-429, 2019.
[7] R. B. Messaoud, “Observer for nonlinear systems
using mean value theorem and particle swarm
optimization algorithm,” ISA Transactions, vol. 85,
pp. 226-236, 2019.
[8] W. Kryszewski and J. Siemianowski, “The Bolzano
mean-value theorem and partial differential
equations,” Journal of Mathematical Analysis and
Applications, vol. 457, pp. 1452-1477, 2018.
[9] T. D. Wooley, “The cubic case of the main conjecture
in Vinogradov's mean value theorem,” Advances in
Mathematics, vol. 294, pp. 532-561, 2016.
[10] J. Li, “Proof of Lagrange mean value theorem and its
application in text design,” Chemical Engineering
Transactions, vol. 51, pp. 325-330, 2016.

A Note on the Generalization of the Mean Value Theorem

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