"Solving problems", writes Polya, "is a practical art, like swimming, or skiing, or playing the piano: You can learn it only by imitation and practice. This book cannot offer you a magic key that opens all the doors and solves all the problems, but it offers you good examples for imitation and many opportunities for practice: If you wish to learn swimming you have to go into the water and if you wish to become a problem solver you have to solve problems." "In enough cases to allay . . . discouragement over not immediately discovering a solution, Professor Polya masterfully leads the reader down several unproductive paths. At the end of each chapter he provides examples for the render to solve. By means of these carefully selected and arranged problems, many of them directly related to others that precede, and guided by just the right suggestions at just the proper time, the reader's own ability is developed and extended. Solutions to the examples and, in many cases, outlines of procedures for discovering solutions. arc given at the back of the book. With striking promise for effectiveness, the entire book as a unit is one great experience in learning processes for problem solving through participation. The author has captured with great success the implication of his basic premise stated in the preface ..." The Mathematics Teacher

Complex Variables

One Infinite Series and Infinite Sequences.- 1 Operations with Power Series.- Additive Number Theory, Combinatorial Problems, and Applications.- Binomial Coefficients and Related Problems.- Differentiation of Power Series.- Functional Equations and Power Series.- Gaussian Binomial Coefficients.- Majorant Series.- 2 Linear Transformations of Series. A Theorem of Cesàro.- Triangular Transformations of Sequences into Sequences.- More General Transformations of Sequences into Sequences.- Transformations of Sequences into Functions. Theorem of Cesàro.- 3 The Structure of Real Sequences and Series.- The Structure of Infinite Sequences.- Convergence Exponent.- The Maximum Term of a Power Series.- Subseries.- Rearrangement of the Terms.- Distribution of the Signs of the Terms.- 4 Miscellaneous Problems.- Enveloping Series.- Various Propositions on Real Series and Sequences.- Partitions of Sets, Cycles in Permutations.- Two Integration.- 1 The Integral as the Limit of a Sum of Rectangles.- The Lower and the Upper Sum.- The Degree of Approximation.- Improper Integrals Between Finite Limits.- Improper Integrals Between Infinite Limits.- Applications to Number Theory.- Mean Values and Limits of Products.- Multiple Integrals.- 2 Inequalities.- Inequalities.- Some Applications of Inequalities.- 3 Some Properties of Real Functions.- Proper Integrals.- Improper Integrals.- Continuous, Differentiate, Convex Functions.- Singular Integrals. Weierstrass' Approximation Theorem.- 4 Various Types of Equidistribution.- Counting Function. Regular Sequences.- Criteria of Equidistribution.- Multiples of an Irrational Number.- Distribution of the Digits in a Table of Logarithms and Related Questions.- Other Types of Equidistribution.- 5 Functions of Large Numbers.- Laplace's Method.- Modifications of the Method.- Asymptotic Evaluation of Some Maxima.- Minimax and Maximin.- Three Functions of One Complex Variable. General Part.- 1 Complex Numbers and Number Sequences.- Regions and Curves. Working with Complex Variables.- Location of the Roots of Algebraic Equations.- Zeros of Polynomials, Continued. A Theorem of Gauss.- Sequences of Complex Numbers.- Sequences of Complex Numbers, Continued: Transformation of Sequences.- Rearrangement of Infinite Series.- 2 Mappings and Vector Fields.- The Cauchy-Riemann Differential Equations.- Some Particular Elementary Mappings.- Vector Fields.- 3 Some Geometrical Aspects of Complex Variables.- Mappings of the Circle. Curvature and Support Function.- Mean Values Along a Circle.- Mappings of the Disk. Area.- The Modular Graph. The Maximum Principle.- 4 Cauchy's Theorem • The Argument Principle.- Cauchy's Formula.- Poisson's and Jensen's Formulas.- The Argument Principle.- Rouche's Theorem.- 5 Sequences of Analytic Functions.- Lagrange's Series. Applications.- The Real Part of a Power Series.- Poles on the Circle of Convergence.- Identically Vanishing Power Series.- Propagation of Convergence.- Convergence in Separated Regions.- The Order of Growth of Certain Sequences of Polynomials.- 6 The Maximum Principle.- The Maximum Principle of Analytic Functions.- Schwarz's Lemma.- Hadamard's Three Circle Theorem.- Harmonic Functions.- The Phragmén-Lindelöf Method.- Author Index.

In 1937 there appeared a paper that was to have a profound influence on the progress of combinatorial enumeration, both in its theoretical and applied aspects. Entitled Kombinatorische Anzahlbest immungen jUr Gruppen, Graphen und chemische Verbindungen, it was published in Acta Mathematica, Vol. 68, pp. 145 to 254. Its author, George Polya, was already a mathematician of considerable stature, well-known for outstanding work in many branches of mathematics, particularly analysis. The paper in Question was unusual in that it depended almost entirely on a single theorem -- the "Hauptsatz" of Section 4 -- a theorem which gave a method for solving a general type of enumera tion problem. On the face of it, this is not something that one would expect to run to over 100 pages. Yet the range of the applica tions of the theorem and of its ramifications was enormous, as Polya clearly showed. In the various sections of his paper he explored many applications to the enumeration of graphs, principally trees, and of chemical isomers, using his theorem to present a comprehen sive and unified treatment of problems which had previously been solved, if at all, only by ad hoc methods. In the final section he investigated the asymptotic properties of these enumerational results, bringing to bear his formidable insight as an analyst.

In the winter of 1978, Professor George P61ya and I jointly taught Stanford University's introductory combinatorics course. This was a great opportunity for me, as I had known of Professor P61ya since having read his classic book, How to Solve It, as a teenager. Working with P6lya, who ·was over ninety years old at the time, was every bit as rewarding as I had hoped it would be. His creativity, intelligence, warmth and generosity of spirit, and wonderful gift for teaching continue to be an inspiration to me. Combinatorics is one of the branches of mathematics that play a crucial role in computer sCience, since digital computers manipulate discrete, finite objects. Combinatorics impinges on computing in two ways. First, the properties of graphs and other combinatorial objects lead directly to algorithms for solving graph-theoretic problems, which have widespread application in non-numerical as well as in numerical computing. Second, combinatorial methods provide many analytical tools that can be used for determining the worst-case and expected performance of computer algorithms. A knowledge of combinatorics will serve the computer scientist well. Combinatorics can be classified into three enumerative, eXistential, and constructive. Enumerative combinatorics deals with the counting of combinatorial objects. Existential combinatorics studies the existence or nonexistence of combinatorial configurations.