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Complex Variables
and
Numerical Methods
Gujarat Technological University 2017
Second Edition
About the Authors
Ravish R Singh is presently Academic Advisor at Thakur
Educational Trust, Mumbai. He obtained a BE degree from
University of Mumbai in 1991, an MTech degree from IIT
Bombay in 2001, and a PhD degree from Faculty of Technology,
University of Mumbai, in 2013. He has published several books
with McGraw Hill Education (India) Private Limited on varied
subjects like Engineering Mathematics (I and II), Applied
Mathematics, Electrical Engineering, Electrical and Electronics
Engineering, etc., for all-India curricula as well as regional
curricula of some universities like Gujarat Technological University, Mumbai University,
Pune University, Jawaharlal Nehru Technological University, Anna University,
Uttarakhand Technical University, and Dr A P J Abdul Kalam Technical University
(formerly known as UPTU). Dr Singh is a member of IEEE, ISTE, and IETE, and has
published research papers in national and international journals. His fields of interest
include Circuits, Signals and Systems, and Engineering Mathematics.
Ravish R Singh
Academic Advisor
Thakur Educational Trust
Mumbai, Maharashtra
Mukul Bhatt
Assistant Professor
Department of Humanities and Sciences
Thakur College of Engineering and Technology
Mumbai, Maharashtra
Information contained in this work has been obtained by McGraw Hill Education (India), from sources
believed to be reliable. However, neither McGraw Hill Education (India) nor its authors guarantee the accuracy
or completeness of any information published herein, and neither McGraw Hill Education (India) nor its
authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This
work is published with the understanding that McGraw Hill Education (India) and its authors are supplying
information but are not attempting to render engineering or other professional services. If such services are
required, the assistance of an appropriate professional should be sought.
Typeset at Text-o-Graphics, B-1/56, Aravali Apartment, Sector-34, Noida 201 301, and printed at
Cover Printer:
7. Interpolation 7.1–7.88
7.1 Introduction 7.1
7.2 Finite Differences 7.2
7.3 Different Operators and their Relations 7.6
7.4 Interpolation 7.19
7.5 Newton’s Forward Interpolation Formula 7.19
7.6 Newton’s Backward Interpolation Formula 7.30
7.7 Central Difference Interpolation 7.39
7.8 Gauss’s Forward Interpolation Formula 7.40
7.9 Gauss’s Backward Interpolation Formula 7.44
7.10 Stirling’s Formula 7.48
7.11 Interpolation with Unequal Intervals 7.55
7.12 Lagrange’s Interpolation Formula 7.56
7.13 Divided Differences 7.70
7.14 Newton’s Divided Difference Formula 7.71
7.15 Inverse Interpolation 7.84
Points to Remember 7.86
8. Numerical Integration 8.1–8.41
8.1 Introduction 8.1
8.2 Newton–Cotes Quadrature Formula 8.1
8.3 Trapezoidal Rule 8.2
8.4 Simpson’s 1/3 Rule 8.9
8.5 Simpson’s 3/8 Rule 8.19
8.6 Gaussian Quadrature Formulae 8.31
Points to Remember 8.40
9. Solutions of a System of Linear Equations 9.1–9.62
9.1 Introduction 9.1
9.2 Solutions of a System of Linear Equations 9.2
9.3 Elementary Transformations 9.2
9.4 Numerical Methods for Solutions of a System of Linear Equations 9.3
9.5 Gauss Elimination Method 9.4
9.6 Gauss Elimination Method with Partial Pivoting 9.15
9.7 Gauss–Jordan Method 9.20
9.8 Gauss–Jacobi Method 9.31
9.9 Gauss–Siedel Method 9.37
Points to Remember 9.61
10. Roots of Algebraic and Transcendental Equations 10.1–10.50
10.1 Introduction 10.1
10.2 Bisection Method 10.2
10.3 Regula Falsi Method 10.15
10.4 Newton–Raphson Method 10.22
x Contents
Index I.1–I.2
Preface
Mathematics is a key area of study in any engineering course. A sound knowledge
of this subject will help engineering students develop analytical skills, and thus
enable them to solve numerical problems encountered in real life, as well as apply
mathematical principles to physical problems, particularly in the field of engineering.
Users
This book is designed for the 4th semester GTU Mechanical Engineering students
pursuing the course Complex Variables and Numerical Methods (CODE 2141905). It
covers the complete GTU syllabus for the course on Complex Variables and Numerical
Methods for the mechanical engineering branch.
Objective
The crisp and complete explanation of topics will help students easily understand the
basic concepts. The tutorial approach (i.e., teach by example) followed in the text will
enable students develop a logical perspective to solving problems.
Features
Each topic has been explained from the examination point of view, wherein the theory
is presented in an easy-to-understand student-friendly style. Full coverage of concepts
is supported by numerous solved examples with varied complexity levels, which is
aligned to the latest GTU syllabus. Fundamental and sequential explanation of topics
is well aided by examples and exercises. The solutions of examples are set following a
‘tutorial’ approach, which will make it easy for students from any background to easily
grasp the concepts. Exercises with answers immediately follow the solved examples
enforcing a practice-based approach. We hope that the students will gain logical under-
standing from solved problems and then reiterate it through solving similar exercise
problems themselves. The unique blend of theory and application caters to the require-
ments of both the students and the faculty. Solutions of GTU examination questions
are incorporated within the text appropriately.
xii Preface
Highlights
∑ Crisp content strictly as per the latest GTU syllabus of Complex Variables and
Numerical Methods (Regulation 2014)
∑ Comprehensive coverage with lucid presentation style
∑ Each section concludes with an exercise to test understanding of topics
∑ Solutions of GTU examination papers from 2010 to 2015 present appropriately
within the chapters
∑ Solution of 2016 GTU examination paper can be accessible through weblink.
∑ Rich exam-oriented pedagogy:
ã Solved Examples within chapters: 473
ã Solved GTU questions tagged within chapters: 150
ã Unsolved Exercises: 474
Chapter Organization
The content spans the following twelve chapters which wholly and sequentially cover
each module of the syllabus.
o Chapter 1 introduces Complex Numbers.
o Chapter 2 discusses Analytic Functions.
o Chapter 3 presents Complex Integration.
o Chapter 4 covers Power Series.
o Chapter 5 deals with Applications of Contour Integration.
o Chapter 6 presents Conformal Mapping and its Applications.
o Chapter 7 explains Interpolation.
o Chapter 8 introduces Numerical Integration.
o Chapter 9 discusses Solutions of a System of Linear Equations.
o Chapter 10 deals with Roots of Algebraic and Transcendental Equations.
o Chapter 11 covers Eigenvalues by Power and Jacobi Methods.
o Chapter 12 explains Numerical Solution of Ordinary Differential Equations.
Acknowledgements
We are grateful to the following reviewers who reviewed various chapters of the script
and generously shared their valuable comments:
We would also like to thank all the staff at McGraw Hill Education (India), especially
Piyali Chatterjee, Anuj Kr. Shriwastava, Koyel Ghosh, Satinder Singh Baveja,
and Vibha Mahajan for coordinating with us during the editorial, copyediting, and
production stages of this book.
Our acknowledgements would be incomplete without a mention of the contribution of
all our family members. We extend a heartfelt thanks to them for always motivating
and supporting us throughout the project.
Constructive suggestions for the improvement of the book will always be welcome.
Ravish R Singh
Mukul Bhatt
Publisher’s Note
Remember to write to us. We look forward to receiving your feedback,
comments, and ideas to enhance the quality of this book. You can reach us at
info.india@mheducation.com. Please mention the title and authors’ name as the
subject. In case you spot piracy of this book, please do let us know.
RoAdmAP to the SyllAbuS
This text is useful for
Complex Variables and Numerical Methods (CoDe 2141905)
GO TO
CHAPTER 1: Complex Numbers
CHAPTER 2: Analytic Functions
GO TO
CHAPTER 3: Complex Integration
GO TO
CHAPTER 4: Power Series
xvi Roadmap to the Syllabus
GO TO
CHAPTER 5: Applications of Contour Integration
GO TO
CHAPTER 6: Conformal Mapping and its Applications
Module 6: Interpolation
Interpolation: Finite Differences, Forward, Backward and Central Operators,
Interpolation by Polynomials: Newton’s forward, Backward Interpolation
Formulae, Newton’s Divided Formula, Gauss and Stirling’s Central Difference
Formulae and Lagrange’s Interpolation Formulae for Unequal Intervals
GO TO
CHAPTER 7: Interpolation
GO TO
CHAPTER 8: Numerical Integration
GO TO
CHAPTER 9: Solutions of a System of Linear Equations
Roadmap to the Syllabus xvii
GO TO
CHAPTER 10: Roots of Algebraic and Transcendental Equations
Module 10:
Eigenvalues by Power and Jacobi Methods
GO TO
CHAPTER 11: Eigenvalues by Power and Jacobi Methods
GO TO
CHAPTER 12: Numerical Solution of Ordinary Differential
Equations
CHAPTER
Complex
1
Numbers
chapter outline
1.1 Introduction
1.2 Complex Numbers
1.3 Geometrical Representation of Complex Numbers (Argand’s Diagram)
1.4 Algebra of Complex Numbers
1.5 Different Forms of Complex Numbers
1.6 Modulus and Argument (or Amplitude) of Complex Numbers
1.7 Properties of Complex Numbers
1.8 De Moivre’s Theorem
1.9 Applications of De Moivre’s Theorem
1.10 Circular and Hyperbolic Functions
1.11 Inverse Hyperbolic Functions
1.12 Separation into Real and Imaginary Parts
1.13 Logarithm of a Complex Number
1.1 IntroductIon
The complex numbers are an extension of the real numbers obtained by introducing
an imaginary unit i, where i = -1 . The operations of addition, subtraction,
multiplication, and division are applicable on complex numbers. A negative real
number can be obtained by squaring a complex number. With a complex number,
it is always possible to find solutions to polynomial equations of degree more than
one. Complex numbers are used in many applications, such as control theory, signal
analysis, quantum mechanics, relativity, etc.
1.2 Chapter 1 Complex Numbers
Let z = x + iy
= r (cos q + i sin q )
||
Here ‘r’ is called the modulus or absolute value of z and is denoted by z or mod (z) and
q is called argument or amplitude of z and is denoted by arg (z) or amp (z).
Hence, z = r = x 2 + y2
Ê yˆ
arg (z) = q = tan -1 Á ˜
Ë x¯
note The value of q lying between –p and p is called the principal value of argu-
ment. The argument of z is the value of q which lies in the quadrant of point (x, y).
Êz ˆ z
(e) Á 1 ˜ = 1
Ë z2 ¯ z2
(f ) z z = z 2 = | z |2 È∵| z | = | z | = x 2 + y 2 ˘
|| ÎÍ ˚˙
(g) |z1z2| = |z1| |z2|
and arg (z1z2) = arg (z1) + arg (z2)
z1 z1
(h) =
z2 z2
Êz ˆ
and arg Á 1 ˜ = arg (z1) – arg (z2)
Ë z2 ¯
1.7 Properties of Complex Numbers 1.5
example 1
Arg (z1, z2) = Arg (z1) + Arg (z2)? Justify. [Summer 2015]
Solution
Yes, Arg (z1 z2) = Arg (z1) + Arg (z2)
example 2
-2
Find the principal argument Arg z when z = . [Winter 2014]
1+ 3 i
Solution
-2
z=
1+ 3 i
=
-2
◊
(1 - 3 i)
1 + 3i (1 - 3 i)
-2 + 2 3 i
=
1+ 3
1 3
=- +i
2 2
Ê 3ˆ
ÁË ˜
2 ¯
Arg z = tan -1
Ê 1ˆ
ÁË - ˜¯
2
( )
= tan -1 - 3
2p
=
3
1.6 Chapter 1 Complex Numbers
example 3
Find the modulus and principal value of the arguments of the following
complex numbers:
(
(i) (4 + 2i ) -3 + 2i )
(ii) 2 + 6 3i
5 + 3i
Solution
(i) z = (4 + 2i ) ( -3 + 2i )
= ( -12 + 4 2i - 6i - 2 2 )
= - (12 + 2 2 ) + i ( 4 2 - 6 )
|z| = (12 + 2 2 )2 + (4 2 - 6)
2
= 2 36 + 2 + 12 2 + 8 + 9 - 12 2
= 2 55
È 4 2 -6 ˘
arg( z ) = tan -1 Í ˙
ÍÎ - (12 + 2 2 ) ˙˚
Ê 3-2 2 ˆ
= tan -1 Á ˜
Ë 6+ 2 ¯
Aliter
z = (4 + 2i ) ( -3 + 2i ) = z1 z2 , say
r =|z|
= z1 z2
= z1 z2
= 4 + 2i -3 + 2i
= ( 16 + 4 ) ( 9 + 2 )
= 220
= 2 55
q = arg( z )
= arg( z1 z2 )
= arg( z1 ) + arg( z2 )
= arg(4 + 2i ) + arg ( -3 + 2i )
1.7 Properties of Complex Numbers 1.7
Ê 2ˆ Ê 2ˆ
= tan -1 Á ˜ + tan -1 Á
Ë 4¯ Ë -3 ˜¯
Ê 1ˆ Ê 2ˆ
= tan -1 Á ˜ - tan -1 Á
Ë 2¯ Ë 3 ˜¯
Ê 1 2 ˆ
-1
Á 2- 3 ˜
= tan Á ˜
Á 1+ 1 ◊ 2 ˜
ÁË ˜¯
2 3
Ê 3-2 2 ˆ
= tan -1 Á
Ë 6 + 2 ˜¯
2 + 6 3i
z=
(ii) 5 + 3i
Ê 2 + 6 3i ˆ Ê 5 - 3i ˆ
=Á ˜Á ˜
Ë 5 + 3i ¯ Ë 5 - 3i ¯
28 + 28 3i
=
28
= 1 + 3i
( 3)
2
| z | = (1)2 + =2
Ê 3ˆ p
arg ( z ) = tan -1 Á =
Ë 1 ˜¯ 3
example 4
Evaluate [(1+i)100 + (1–i)100].
Solution
Let 1 + i = reiq
r = 1+ i = 1+1 = 2
Ê 1ˆ p
q = tan -1 Á ˜ = tan -1 1 =
Ë 1¯ 4
p
i
\ 1 + i = 2e 4
p
-i
and 1 - i = 2e 4
1.8 Chapter 1 Complex Numbers
100 100
Ê i ˆ
p Ê -i ˆ
p
(1 + i )
100
+ (1 - i )
100
= Á 2e 4 ˜ + Á 2e 4 ˜
Ë ¯ Ë ¯
example 5
Express in polar form:
2
Ê 2 + iˆ
(i) Á (ii) 1 + sin a + i cos a
Ë 3 - i ˜¯
Solution
2
Ê 2 +iˆ 4 + i 2 + 4i
(i) ÁË 3 - i ˜¯ =
9 + i 2 - 6i
3 + 4i
=
8 - 6i
3 + 4i 8 + 6i
= ◊
8 - 6i 8 + 6i
i
=
2
1
= 0+i◊
2
1
Let 0+i◊ = r (cos q + i sin q )
2
2
Ê 1ˆ 1
r = 02 + Á ˜ =
Ë 2¯ 2
Ê 1ˆ
Á ˜ p
and q = tan -1 Á 2 ˜ = tan -1 • =
Ë 0¯ 2
Hence, the polar form is
2
Ê 2 +iˆ 1Ê p pˆ
ÁË 3 - i ˜¯ = 2 ÁË cos 2 + i sin 2 ˜¯
1.7 Properties of Complex Numbers 1.9
Êp ˆ Êp ˆ
(ii) 1 + sin a + i cos a = 1 + cos Á - a ˜ + i sin Á - a ˜
Ë2 ¯ Ë2 ¯
Êp aˆ Êp aˆ Êp aˆ
= 2 cos2 Á - ˜ + 2i sin Á − ˜ cos Á - ˜
Ë 4 2¯ Ë 4 2¯ Ë 4 2¯
È 2 q q q˘
Í∵ 1 + cos q = 2 cos 2 , sin q = 2 sin 2 cos 2 ˙
Î ˚
Êp aˆ È Êp aˆ Ê p a ˆ˘
= 2 cos Á - ˜ Ícos Á - ˜ + i sin Á - ˜ ˙
Ë 4 2¯ Î Ë 4 2¯ Ë 4 2 ¯˚
example 6
Find the value of - 5 + 12i .
Solution
Let - 5 + 12i = x + iy
–5 + 12i = (x + iy)2
–5 + 12i = (x2 – y2) + i (2xy)
Comparing real and imaginary parts,
x2 – y2 = –5 ... (1)
and 2xy = 12
xy = 6
6
Putting y = in Eq. (1),
x
36
x2 - = –5
x2
1.10 Chapter 1 Complex Numbers
x4 + 5x2 – 36 = 0
(x2 + 9) (x2 – 4) = 0
x2 = –9, x2 = 4
Since x is real, x=±2
and y=±3
Hence, -5 + 12i = ± 2 ± 3i
example 7
iy 3 y + 4i
If x and y are real, solve the equation - = 0.
ix + 1 3 x + y
Solution
iy 3 y + 4i
- =0
ix + 1 3 x + y
iy (3 x + y) - (3 y + 4i )(ix + 1)
=0
(ix + 1)(3 x + y)
(-3 y + 4 x ) + i (3 xy + y 2 - 3 xy - 4) = 0 + i 0
(-3 y + 4 x ) + i( y 2 - 4) = 0 + i 0
example 8
Solve the equation z2 + (2i – 3) z + 5 – i = 0. [Summer 2015]
Solution
z2 + (2i – 3) z + 5 – i = 0
1.7 Properties of Complex Numbers 1.11
example 9
Prove that Re (z) > 0 and |z – 1| < |z + 1| are equivalent, where
z = x + iy.
Solution
z = x + iy
Re (z) > 0
x>0 ... (1)
Now, |z – 1| < |z + 1|
|x + iy – 1| < |x + iy + 1|
( x − 1) 2 + y 2 < ( x + 1) 2 + y 2
x2 + 1 – 2x + y2 < x2 + 1 + 2x + y2
–2x < 2x
0 < 4x
0<x or x>0 ... (2)
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contenteront plus difficilement de leur sort... Par votre compassion,
vous en aurez fait des malheureux.» Vous reconnaissez bien là
toutes les maximes de la tyrannie raisonnable, et de la sage barbarie
des satisfaits... Évidemment, je serais bien plus tranquille si je voyais
les choses d'un peu plus bas, si j'obéissais aveuglément à cette
consigne de solidarité qui nous unit, si je n'essayais pas de me
mettre à la place des ouvriers qui sont en face de nous. Quand on
ne voit qu'un seul côté de la question, on est bien plus à son aise...
Mais on ne se refait pas. Je suis l'homme des concessions et des
transactions. Ainsi, dans mes affaires, je n'ai jamais de procès.
Aussitôt que j'entre en conflit avec quelqu'un, oh! il m'arrive de me
mettre en colère, comme tout le monde, de faire l'imbécile et de
crier: «Je serai intransigeant! Je le traînerai devant les tribunaux!»
Seulement, comme je me suis fait une règle de ne jamais prendre de
décision immédiate, le lendemain, je suis calmé. Et je transige.
C'est ainsi qu'ils se parlaient chaque matin de leurs préoccupations,
et qu'ils évoquaient de graves questions, paisiblement, sans trop
s'émouvoir. C'étaient des entretiens libres et heureux. Quand ils
étaient las d'être assis sur l'herbe, ils reprenaient le chemin du
château. Et Julien montait dans sa chambre pour mettre un pantalon
plus frais, afin de faire honneur à la dame de ses pensées.
CHAPITRE X
Vers l'amie.
Les poètes ne servent pas seulement de truchement aux amoureux.
Ils leur rendent encore ce service aussi important et aussi pratique
de leur fournir des intermèdes pour leurs longs entretiens avec la
femme aimée. Quand on est mal disposé, quand on est à court de
sujets de conversation, un saut à la bibliothèque. Victor Hugo vient
nous dire complaisamment La Tristesse d'Olympio. Vigny, sans se
faire prier, détaille les strophes miraculeuses de la Maison du
Berger. Ou bien, c'est Baudelaire qui, aux alentours du crépuscule,
nous prête son Balcon, à l'effet immanquable.
Julien connaît aussi les poètes actuels. Sa mémoire est munie de
vers tout récents. Il a avec lui le nécessaire de poésie, tout à fait
moderne, dernier cri.
Il possède aussi quelques souvenirs d'enfance qu'il raconte fort bien.
Il parle de sa mère comme si c'était lui qui avait découvert l'amour
filial.
Enfin, il sait faire de fréquentes allusions à son isolement, au besoin
constant de consolation qui le tourmente. Il arrive à parler
couramment de la personne idéale qui écoutera sa souffrance. Et,
quand le soir, on se sépare pour aller se coucher, et qu'il prend
congé d'Antoinette, son serrement de main n'est pas la grossière
pression d'un bellâtre malappris... C'est une étreinte de doigts où l'on
sent tout son désespoir. Il serre la main d'Antoinette comme un
naufragé saisit une branche de la rive. Tous ses gestes savent être
instinctifs, presque inconscients. Il n'adresse à la bien aimée que
des hommages naïfs et éperdus, qu'elle ne peut pas repousser.
Julien n'agit pas avec l'habileté cauteleuse d'un oiseleur qui veut
prendre une proie au piège. Non, mais tous ses efforts sont
naturellement adroits, car il voit clairement le but vers lequel il se
dirige. C'est un homme plein de tact, à qui il ne manque le plus
souvent, pour bien agir, que la volonté d'agir. Cette volonté, il l'a
enfin acquise le jour où, ayant fait entendre à Antoinette qu'il l'aimait,
il s'est donné à lui-même la certitude qu'il était épris de cette femme.
Il n'a plus qu'à obéir à sa volonté, comme Ruy Blas obéissait à Don
Salluste.