An Overview of Logic, Proofs, Set Theory, and Functions Contents
An Overview of Logic, Proofs, Set Theory, and Functions aBa Mbirika and Shanise Walker Contents 1 Numerical Sets and Other Preliminary Symbols3 2 Statements and Truth Tables5 3 Implications 9 4 Predicates and Quantifiers 13 5 Writing Formal Proofs 22 6 Mathematical Induction 29 7 Quick Review of Set Theory & Set Theory Proofs 33 8 Functions, Bijections, Compositions, Etc. 38 9 Solutions to all exercises 42 Index 51 Preface: This handout is meant primarily for those students who are already familiar with most of the subject matter contained within (that is, those who have taken a proofs class before). Its purpose is to provide a foundation as a proofs refresher when taking classes like Real Analysis I or II, Abstract Algebra I or II, Number Theory, Discrete Mathematics, Linear Algebra, etc. LICENSE Creative Commons License (CC BY-NC-SA): This text, including the art and illustrations, are available under the Creative Commons license (CC BY-NC- SA), allowing anyone to reuse, revise, remix and redistribute the text. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/4.0/ Section 1 NUMERICAL SETS AND OTHER PRELIMINARY SYMBOLS Page 3 1 Numerical Sets and Other Preliminary Symbols The following are numerical sets that you should familiarize yourself with: natural numbers 1 N = f1; 2; 3;:::g integers Z = f:::; −3; −2; −1; 0; 1; 2; 3;:::g a rational numbers Q = b j a; b 2 Z and b 6= 0 real numbers R = frational and irrational numbersg p complex numbers C = fa + bi j a; b 2 R and i = −1g p Gaussian integers Z[i] = fa + bi j a; b 2 Z and i = −1g 2πi Eisenstein integers Z[ρ] = fa + bρ j a; b 2 Z and ρ = e 3 g even integers 2Z = f2k j k 2 Zg odd integers 2Z + 1 = f2k + 1 j k 2 Zg arithmetic progression aZ + b = fak + b j k 2 Zg where a; b fixed CULTURAL QUESTION 1: Why are the integers denoted Z? ANSWER: The German word for \numbers" is Zahlen.
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