Your quiz in recitation on Tuesday will cover 3.1: Arguments and inference. Your also have an online quiz, covering 3.1, due by 11:59 p.m., Tuesday.

Size: px
Start display at page:

Download "Your quiz in recitation on Tuesday will cover 3.1: Arguments and inference. Your also have an online quiz, covering 3.1, due by 11:59 p.m., Tuesday."

Transcription

1 Friday, February 15 Today we will begin Course Notes 3.2: Methods of Proof. Your quiz in recitation on Tuesday will cover 3.1: Arguments and inference. Your also have an online quiz, covering 3.1, due by 11:59 p.m., Tuesday. Simple verbal arguments (from 3.1) Validity of symbolic arguments, using truth tables (from 3.1) More Rules of Inference, Fallacies (from 3.1) Inference, deduction (from 3.1) Constructing validity proofs (from 3.1) Rules of inference, quantifiers (from 3.1) Other quantified arguments (from 3.1) More complicated quantified arguments (from 3.1) Still more complicated quantified arguments (from 3.1) True or false: If n is any even number, then n 2 17 must be odd. A. True B. False

2 3.2 Methods of proof We now begin the practice of writing proofs in a context other than formal logic. In the definitions that follow, the assumption is that p and q are specific propositions about objects from mathematics and computer science. Direct proof To prove the proposition p q directly, we assume that the hypothesis p is true, and use that assumption to construct, step-by-step, a logical proof that q must be true. The steps of the proof use definitions, other established facts (theorems), and rules of inference. The proof is an incontrovertible explanation of why q must be true.

3 EXAMPLES 1. Use the definitions of even number, and odd number, to prove/disprove the following conjecture: If n is even, then n 2 17 is odd. First: Definitions An even integer or even number is an integer that is a multiple of 2; more formally: the integer n is even if and only if there exists an integer k such that n = 2k. An odd integer or odd number is the sum of an even number and 1; that is, the integer n is odd if and only if there exists an integer k such that n = 2k + 1. Our proof will proceed is follows: we will show, through calculation, that if n is any arbitrary integer that satisfies the definition of even number, then n 2 17 will satisfy the definition of odd number.

4 Closure Properties of the integers Our proof will also rely on the closure properties of the integers: The integers are closed under addition, subtraction, and multiplication. That is, the sum, difference and product of integers, is an integer. These closure properties are axioms (statements accepted as true, without proof) of the integers.

5 True or false: If x is any rational number, then 1/x is a rational number. A. True B. False

6 Prove or disprove the following conjecture: If x is a rational number and x 0, then 1/x is a rational number. First: Definition The real number x is a rational number if and only if there exist integers a, b, such that x = a/b in lowest terms, and b 0. Note: proving the conjecture will require a formal proof similar to the proof in the previous example. The formal proof will show that the conjecture is true for all nonzero rational numbers. On the other hand, if we suspect that the conjecture is false, then all that is needed to disprove it is a single counterexample. That is, to disprove this conjecture, we only have to find one nonzero rational number x for which the conjecture is not true.

7 Question: Are the rational numbers closed under addition or multiplication? A. The rational numbers closed under addition but not multiplication. B. The rational numbers closed under multiplication but not addition. C. The rational numbers closed under both addition and multiplication. D. The rational numbers closed under neither addition nor multiplication. For each of the two claims, if the claim is true, we should be able to write the proof using the definition of rational number. If the claim is false, we should be able to cite a counterexample proving that the claim is false.

CSE 20 DISCRETE MATH. Winter

CSE 20 DISCRETE MATH. Winter CSE 20 DISCRETE MATH Winter 2017 http://cseweb.ucsd.edu/classes/wi17/cse20-ab/ Today's learning goals Distinguish between a theorem, an axiom, lemma, a corollary, and a conjecture. Recognize direct proofs

More information

The following techniques for methods of proofs are discussed in our text: - Vacuous proof - Trivial proof

The following techniques for methods of proofs are discussed in our text: - Vacuous proof - Trivial proof Ch. 1.6 Introduction to Proofs The following techniques for methods of proofs are discussed in our text - Vacuous proof - Trivial proof - Direct proof - Indirect proof (our book calls this by contraposition)

More information

CSE 20 DISCRETE MATH. Fall

CSE 20 DISCRETE MATH. Fall CSE 20 DISCRETE MATH Fall 2017 http://cseweb.ucsd.edu/classes/fa17/cse20-ab/ Today's learning goals Distinguish between a theorem, an axiom, lemma, a corollary, and a conjecture. Recognize direct proofs

More information

9/5/17. Fermat s last theorem. CS 220: Discrete Structures and their Applications. Proofs sections in zybooks. Proofs.

9/5/17. Fermat s last theorem. CS 220: Discrete Structures and their Applications. Proofs sections in zybooks. Proofs. Fermat s last theorem CS 220: Discrete Structures and their Applications Theorem: For every integer n > 2 there is no solution to the equation a n + b n = c n where a,b, and c are positive integers Proofs

More information

We last time we began introducing equivalency laws.

We last time we began introducing equivalency laws. Monday, January 14 MAD2104 Discrete Math 1 Course website: www/mathfsuedu/~wooland/mad2104 Today we will continue in Course Notes Chapter 22 We last time we began introducing equivalency laws Today we

More information

Section 3.1: Direct Proof and Counterexample 1

Section 3.1: Direct Proof and Counterexample 1 Section 3.1: Direct Proof and Counterexample 1 In this chapter, we introduce the notion of proof in mathematics. A mathematical proof is valid logical argument in mathematics which shows that a given conclusion

More information

The Process of Mathematical Proof

The Process of Mathematical Proof 1 The Process of Mathematical Proof Introduction. Mathematical proofs use the rules of logical deduction that grew out of the work of Aristotle around 350 BC. In previous courses, there was probably an

More information

1.1 Inductive Reasoning filled in.notebook August 20, 2015

1.1 Inductive Reasoning filled in.notebook August 20, 2015 1.1 Inductive Reasoning 1 Vocabulary Natural or Counting Numbers Ellipsis Scientific Method Hypothesis or Conjecture Counterexample 2 Vocabulary Natural or Counting Numbers 1, 2, 3, 4, 5... positive whole

More information

COMP 182 Algorithmic Thinking. Proofs. Luay Nakhleh Computer Science Rice University

COMP 182 Algorithmic Thinking. Proofs. Luay Nakhleh Computer Science Rice University COMP 182 Algorithmic Thinking Proofs Luay Nakhleh Computer Science Rice University 1 Reading Material Chapter 1, Section 3, 6, 7, 8 Propositional Equivalences The compound propositions p and q are called

More information

Argument. whenever all the assumptions are true, then the conclusion is true. If today is Wednesday, then yesterday is Tuesday. Today is Wednesday.

Argument. whenever all the assumptions are true, then the conclusion is true. If today is Wednesday, then yesterday is Tuesday. Today is Wednesday. Logic and Proof Argument An argument is a sequence of statements. All statements but the first one are called assumptions or hypothesis. The final statement is called the conclusion. An argument is valid

More information

Intro to Algebra Today. We will learn names for the properties of real numbers. Homework Next Week. Due Tuesday 45-47/ 15-20, 32-35, 40-41, *28,29,38

Intro to Algebra Today. We will learn names for the properties of real numbers. Homework Next Week. Due Tuesday 45-47/ 15-20, 32-35, 40-41, *28,29,38 Intro to Algebra Today We will learn names for the properties of real numbers. Homework Next Week Due Tuesday 45-47/ 15-20, 32-35, 40-41, *28,29,38 Due Thursday Pages 51-53/ 19-24, 29-36, *48-50, 60-65

More information

Unit 2: Logic and Reasoning. start of unit

Unit 2: Logic and Reasoning. start of unit Unit 2: Logic and Reasoning Prior Unit: Introduction to Geometry Next Unit: Transversals By the end of this unit I will be able to: Skill Self-Rating start of unit Date(s) covered Self-Rating end of unit

More information

Basic Logic and Proof Techniques

Basic Logic and Proof Techniques Chapter 3 Basic Logic and Proof Techniques Now that we have introduced a number of mathematical objects to study and have a few proof techniques at our disposal, we pause to look a little more closely

More information

Chapter 1, Logic and Proofs (3) 1.6. Rules of Inference

Chapter 1, Logic and Proofs (3) 1.6. Rules of Inference CSI 2350, Discrete Structures Chapter 1, Logic and Proofs (3) Young-Rae Cho Associate Professor Department of Computer Science Baylor University 1.6. Rules of Inference Basic Terminology Axiom: a statement

More information

MAT 300 RECITATIONS WEEK 7 SOLUTIONS. Exercise #1. Use induction to prove that for every natural number n 4, n! > 2 n. 4! = 24 > 16 = 2 4 = 2 n

MAT 300 RECITATIONS WEEK 7 SOLUTIONS. Exercise #1. Use induction to prove that for every natural number n 4, n! > 2 n. 4! = 24 > 16 = 2 4 = 2 n MAT 300 RECITATIONS WEEK 7 SOLUTIONS LEADING TA: HAO LIU Exercise #1. Use induction to prove that for every natural number n 4, n! > 2 n. Proof. For any n N with n 4, let P (n) be the statement n! > 2

More information

Predicate Logic. Andreas Klappenecker

Predicate Logic. Andreas Klappenecker Predicate Logic Andreas Klappenecker Predicates A function P from a set D to the set Prop of propositions is called a predicate. The set D is called the domain of P. Example Let D=Z be the set of integers.

More information

MATH CSE20 Homework 5 Due Monday November 4

MATH CSE20 Homework 5 Due Monday November 4 MATH CSE20 Homework 5 Due Monday November 4 Assigned reading: NT Section 1 (1) Prove the statement if true, otherwise find a counterexample. (a) For all natural numbers x and y, x + y is odd if one of

More information

Math.3336: Discrete Mathematics. Proof Methods and Strategy

Math.3336: Discrete Mathematics. Proof Methods and Strategy Math.3336: Discrete Mathematics Proof Methods and Strategy Instructor: Dr. Blerina Xhabli Department of Mathematics, University of Houston https://www.math.uh.edu/ blerina Email: blerina@math.uh.edu Fall

More information

Meaning of Proof Methods of Proof

Meaning of Proof Methods of Proof Mathematical Proof Meaning of Proof Methods of Proof 1 Dr. Priya Mathew SJCE Mysore Mathematics Education 4/7/2016 2 Introduction Proposition: Proposition or a Statement is a grammatically correct declarative

More information

Proof Terminology. Technique #1: Direct Proof. Learning objectives. Proof Techniques (Rosen, Sections ) Direct Proof:

Proof Terminology. Technique #1: Direct Proof. Learning objectives. Proof Techniques (Rosen, Sections ) Direct Proof: Proof Terminology Proof Techniques (Rosen, Sections 1.7 1.8) TOPICS Direct Proofs Proof by Contrapositive Proof by Contradiction Proof by Cases Theorem: statement that can be shown to be true Proof: a

More information

Propositional Calculus. Problems. Propositional Calculus 3&4. 1&2 Propositional Calculus. Johnson will leave the cabinet, and we ll lose the election.

Propositional Calculus. Problems. Propositional Calculus 3&4. 1&2 Propositional Calculus. Johnson will leave the cabinet, and we ll lose the election. 1&2 Propositional Calculus Propositional Calculus Problems Jim Woodcock University of York October 2008 1. Let p be it s cold and let q be it s raining. Give a simple verbal sentence which describes each

More information

Analysis of California Mathematics standards to Common Core standards Algebra I

Analysis of California Mathematics standards to Common Core standards Algebra I Analysis of California Mathematics standards to Common Core standards Algebra I CA Math Standard Domain Common Core Standard () Alignment Comments in 1.0 Students identify and use the arithmetic properties

More information

MCS-236: Graph Theory Handout #A4 San Skulrattanakulchai Gustavus Adolphus College Sep 15, Methods of Proof

MCS-236: Graph Theory Handout #A4 San Skulrattanakulchai Gustavus Adolphus College Sep 15, Methods of Proof MCS-36: Graph Theory Handout #A4 San Skulrattanakulchai Gustavus Adolphus College Sep 15, 010 Methods of Proof Consider a set of mathematical objects having a certain number of operations and relations

More information

CSE 20 DISCRETE MATH. Fall

CSE 20 DISCRETE MATH. Fall CSE 20 DISCRETE MATH Fall 2017 http://cseweb.ucsd.edu/classes/fa17/cse20-ab/ Today's learning goals Describe and use algorithms for integer operations based on their expansions Relate algorithms for integer

More information

MATH 215 Final. M4. For all a, b in Z, a b = b a.

MATH 215 Final. M4. For all a, b in Z, a b = b a. MATH 215 Final We will assume the existence of a set Z, whose elements are called integers, along with a well-defined binary operation + on Z (called addition), a second well-defined binary operation on

More information

Show Your Work! Point values are in square brackets. There are 35 points possible. Tables of tautologies and contradictions are on the last page.

Show Your Work! Point values are in square brackets. There are 35 points possible. Tables of tautologies and contradictions are on the last page. Formal Methods Midterm 1, Spring, 2007 Name Show Your Work! Point values are in square brackets. There are 35 points possible. Tables of tautologies and contradictions are on the last page. 1. Use truth

More information

1.1 Language and Logic

1.1 Language and Logic c Oksana Shatalov, Spring 2018 1 1.1 Language and Logic Mathematical Statements DEFINITION 1. A proposition is any declarative sentence (i.e. it has both a subject and a verb) that is either true or false,

More information

Chapter 1 Elementary Logic

Chapter 1 Elementary Logic 2017-2018 Chapter 1 Elementary Logic The study of logic is the study of the principles and methods used in distinguishing valid arguments from those that are not valid. The aim of this chapter is to help

More information

1.1 Language and Logic

1.1 Language and Logic c Oksana Shatalov, Fall 2017 1 1.1 Language and Logic Mathematical Statements DEFINITION 1. A proposition is any declarative sentence (i.e. it has both a subject and a verb) that is either true or false,

More information

Mathematical Reasoning Rules of Inference & Mathematical Induction. 1. Assign propositional variables to the component propositional argument.

Mathematical Reasoning Rules of Inference & Mathematical Induction. 1. Assign propositional variables to the component propositional argument. Mathematical Reasoning Rules of Inference & Mathematical Induction Example. If I take the day off it either rains or snows 2. When It rains, my basement floods 3. When the basement floods or it snows,

More information

Section 2.1: Introduction to the Logic of Quantified Statements

Section 2.1: Introduction to the Logic of Quantified Statements Section 2.1: Introduction to the Logic of Quantified Statements In the previous chapter, we studied a branch of logic called propositional logic or propositional calculus. Loosely speaking, propositional

More information

Discrete Mathematics & Mathematical Reasoning Predicates, Quantifiers and Proof Techniques

Discrete Mathematics & Mathematical Reasoning Predicates, Quantifiers and Proof Techniques Discrete Mathematics & Mathematical Reasoning Predicates, Quantifiers and Proof Techniques Colin Stirling Informatics Some slides based on ones by Myrto Arapinis Colin Stirling (Informatics) Discrete Mathematics

More information

Correlation: California State Curriculum Standards of Mathematics for Grade 6 SUCCESS IN MATH: BASIC ALGEBRA

Correlation: California State Curriculum Standards of Mathematics for Grade 6 SUCCESS IN MATH: BASIC ALGEBRA Correlation: California State Curriculum Standards of Mathematics for Grade 6 To SUCCESS IN MATH: BASIC ALGEBRA 1 ALGEBRA AND FUNCTIONS 1.0 Students write verbal expressions and sentences as algebraic

More information

Proofs: A General How To II. Rules of Inference. Rules of Inference Modus Ponens. Rules of Inference Addition. Rules of Inference Conjunction

Proofs: A General How To II. Rules of Inference. Rules of Inference Modus Ponens. Rules of Inference Addition. Rules of Inference Conjunction Introduction I Proofs Computer Science & Engineering 235 Discrete Mathematics Christopher M. Bourke cbourke@cse.unl.edu A proof is a proof. What kind of a proof? It s a proof. A proof is a proof. And when

More information

Proofs of Mathema-cal Statements. A proof is a valid argument that establishes the truth of a statement.

Proofs of Mathema-cal Statements. A proof is a valid argument that establishes the truth of a statement. Section 1.7 Proofs of Mathema-cal Statements A proof is a valid argument that establishes the truth of a statement. Terminology A theorem is a statement that can be shown to be true using: definitions

More information

5. Use a truth table to determine whether the two statements are equivalent. Let t be a tautology and c be a contradiction.

5. Use a truth table to determine whether the two statements are equivalent. Let t be a tautology and c be a contradiction. Statements Compounds and Truth Tables. Statements, Negations, Compounds, Conjunctions, Disjunctions, Truth Tables, Logical Equivalence, De Morgan s Law, Tautology, Contradictions, Proofs with Logical Equivalent

More information

CSE 20 DISCRETE MATH WINTER

CSE 20 DISCRETE MATH WINTER CSE 20 DISCRETE MATH WINTER 2016 http://cseweb.ucsd.edu/classes/wi16/cse20-ab/ Today's learning goals Evaluate which proof technique(s) is appropriate for a given proposition Direct proof Proofs by contraposition

More information

CSE 20 DISCRETE MATH SPRING

CSE 20 DISCRETE MATH SPRING CSE 20 DISCRETE MATH SPRING 2016 http://cseweb.ucsd.edu/classes/sp16/cse20-ac/ Today's learning goals Evaluate which proof technique(s) is appropriate for a given proposition Direct proof Proofs by contraposition

More information

Logic Overview, I. and T T T T F F F T F F F F

Logic Overview, I. and T T T T F F F T F F F F Logic Overview, I DEFINITIONS A statement (proposition) is a declarative sentence that can be assigned a truth value T or F, but not both. Statements are denoted by letters p, q, r, s,... The 5 basic logical

More information

Lecture 3. Logic Predicates and Quantified Statements Statements with Multiple Quantifiers. Introduction to Proofs. Reading (Epp s textbook)

Lecture 3. Logic Predicates and Quantified Statements Statements with Multiple Quantifiers. Introduction to Proofs. Reading (Epp s textbook) Lecture 3 Logic Predicates and Quantified Statements Statements with Multiple Quantifiers Reading (Epp s textbook) 3.1-3.3 Introduction to Proofs Reading (Epp s textbook) 4.1-4.2 1 Propositional Functions

More information

Some Review Problems for Exam 1: Solutions

Some Review Problems for Exam 1: Solutions Math 3355 Fall 2018 Some Review Problems for Exam 1: Solutions Here is my quick review of proof techniques. I will focus exclusively on propositions of the form p q, or more properly, x P (x) Q(x) or x

More information

Geometry: Notes

Geometry: Notes Geometry: 2.1-2.3 Notes NAME 2.1 Be able to write all types of conditional statements. Date: Define Vocabulary: conditional statement if-then form hypothesis conclusion negation converse inverse contrapositive

More information

Solution Set 2. Problem 1. [a] + [b] = [a + b] = [b + a] = [b] + [a] ([a] + [b]) + [c] = [a + b] + [c] = [a + b + c] = [a] + [b + c] = [a] + ([b + c])

Solution Set 2. Problem 1. [a] + [b] = [a + b] = [b + a] = [b] + [a] ([a] + [b]) + [c] = [a + b] + [c] = [a + b + c] = [a] + [b + c] = [a] + ([b + c]) Solution Set Problem 1 (1) Z/nZ is the set of equivalence classes of Z mod n. Equivalence is determined by the following rule: [a] = [b] if and only if b a = k n for some k Z. The operations + and are

More information

Algebra 1. Standard 1: Operations With Real Numbers Students simplify and compare expressions. They use rational exponents and simplify square roots.

Algebra 1. Standard 1: Operations With Real Numbers Students simplify and compare expressions. They use rational exponents and simplify square roots. Standard 1: Operations With Real Numbers Students simplify and compare expressions. They use rational exponents and simplify square roots. A1.1.1 Compare real number expressions. A1.1.2 Simplify square

More information

Math 3320 Foundations of Mathematics

Math 3320 Foundations of Mathematics Math 3320 Foundations of Mathematics Chapter 1: Fundamentals Jesse Crawford Department of Mathematics Tarleton State University (Tarleton State University) Chapter 1 1 / 55 Outline 1 Section 1.1: Why Study

More information

Department of Computer Science University at Albany, State University of New York Solutions to Sample Discrete Mathematics Examination I (Spring 2008)

Department of Computer Science University at Albany, State University of New York Solutions to Sample Discrete Mathematics Examination I (Spring 2008) Department of Computer Science University at Albany, State University of New York Solutions to Sample Discrete Mathematics Examination I (Spring 2008) Problem 1: Suppose A, B, C and D are arbitrary sets.

More information

Strategies for Proofs

Strategies for Proofs G. Carl Evans University of Illinois Summer 2013 Today Practice with proofs Become familiar with various strategies for proofs Review: proving universal statements Claim: For any integer a, if a is odd,

More information

Logic. Definition [1] A logic is a formal language that comes with rules for deducing the truth of one proposition from the truth of another.

Logic. Definition [1] A logic is a formal language that comes with rules for deducing the truth of one proposition from the truth of another. Math 0413 Appendix A.0 Logic Definition [1] A logic is a formal language that comes with rules for deducing the truth of one proposition from the truth of another. This type of logic is called propositional.

More information

WUCT121. Discrete Mathematics. Logic. Tutorial Exercises

WUCT121. Discrete Mathematics. Logic. Tutorial Exercises WUCT11 Discrete Mathematics Logic Tutorial Exercises 1 Logic Predicate Logic 3 Proofs 4 Set Theory 5 Relations and Functions WUCT11 Logic Tutorial Exercises 1 Section 1: Logic Question1 For each of the

More information

Homework 3: Solutions

Homework 3: Solutions Homework 3: Solutions ECS 20 (Fall 2014) Patrice Koehl koehl@cs.ucdavis.edu October 16, 2014 Exercise 1 Show that this implication is a tautology, by using a table of truth: [(p q) (p r) (q r)] r. p q

More information

UNIVERSITY OF VICTORIA DECEMBER EXAMINATIONS MATH 122: Logic and Foundations

UNIVERSITY OF VICTORIA DECEMBER EXAMINATIONS MATH 122: Logic and Foundations UNIVERSITY OF VICTORIA DECEMBER EXAMINATIONS 2013 MATH 122: Logic and Foundations Instructor and section (check one): K. Mynhardt [A01] CRN 12132 G. MacGillivray [A02] CRN 12133 NAME: V00#: Duration: 3

More information

1. Introduction to commutative rings and fields

1. Introduction to commutative rings and fields 1. Introduction to commutative rings and fields Very informally speaking, a commutative ring is a set in which we can add, subtract and multiply elements so that the usual laws hold. A field is a commutative

More information

Lecture 2: Proof Techniques Lecturer: Lale Özkahya

Lecture 2: Proof Techniques Lecturer: Lale Özkahya BBM 205 Discrete Mathematics Hacettepe University http://web.cs.hacettepe.edu.tr/ bbm205 Lecture 2: Proof Techniques Lecturer: Lale Özkahya Resources: Kenneth Rosen, Discrete Mathematics and App. cs.colostate.edu/

More information

Sec$on Summary. Mathematical Proofs Forms of Theorems Trivial & Vacuous Proofs Direct Proofs Indirect Proofs

Sec$on Summary. Mathematical Proofs Forms of Theorems Trivial & Vacuous Proofs Direct Proofs Indirect Proofs Section 1.7 Sec$on Summary Mathematical Proofs Forms of Theorems Trivial & Vacuous Proofs Direct Proofs Indirect Proofs Proof of the Contrapositive Proof by Contradiction 2 Proofs of Mathema$cal Statements

More information

THE LOGIC OF QUANTIFIED STATEMENTS. Predicates and Quantified Statements I. Predicates and Quantified Statements I CHAPTER 3 SECTION 3.

THE LOGIC OF QUANTIFIED STATEMENTS. Predicates and Quantified Statements I. Predicates and Quantified Statements I CHAPTER 3 SECTION 3. CHAPTER 3 THE LOGIC OF QUANTIFIED STATEMENTS SECTION 3.1 Predicates and Quantified Statements I Copyright Cengage Learning. All rights reserved. Copyright Cengage Learning. All rights reserved. Predicates

More information

California: Algebra 1

California: Algebra 1 Algebra Discovering Algebra An Investigative Approach California: Algebra 1 Grades Eight Through Twelve Mathematics Content Standards 1.0 Students identify and use the arithmetic properties of subsets

More information

Mathematics 220 Homework 4 - Solutions. Solution: We must prove the two statements: (1) if A = B, then A B = A B, and (2) if A B = A B, then A = B.

Mathematics 220 Homework 4 - Solutions. Solution: We must prove the two statements: (1) if A = B, then A B = A B, and (2) if A B = A B, then A = B. 1. (4.46) Let A and B be sets. Prove that A B = A B if and only if A = B. Solution: We must prove the two statements: (1) if A = B, then A B = A B, and (2) if A B = A B, then A = B. Proof of (1): Suppose

More information

1 The Foundation: Logic and Proofs

1 The Foundation: Logic and Proofs 1 The Foundation: Logic and Proofs 1.1 Propositional Logic Propositions( 명제 ) a declarative sentence that is either true or false, but not both nor neither letters denoting propositions p, q, r, s, T:

More information

ELEMENTARY NUMBER THEORY AND METHODS OF PROOF

ELEMENTARY NUMBER THEORY AND METHODS OF PROOF CHAPTER 4 ELEMENTARY NUMBER THEORY AND METHODS OF PROOF Copyright Cengage Learning. All rights reserved. SECTION 4.6 Indirect Argument: Contradiction and Contraposition Copyright Cengage Learning. All

More information

Two hours. Note that the last two pages contain inference rules for natural deduction UNIVERSITY OF MANCHESTER SCHOOL OF COMPUTER SCIENCE

Two hours. Note that the last two pages contain inference rules for natural deduction UNIVERSITY OF MANCHESTER SCHOOL OF COMPUTER SCIENCE COMP 0 Two hours Note that the last two pages contain inference rules for natural deduction UNIVERSITY OF MANCHESTER SCHOOL OF COMPUTER SCIENCE Mathematical Techniques for Computer Science Date: Friday

More information

Writing proofs for MATH 61CM, 61DM Week 1: basic logic, proof by contradiction, proof by induction

Writing proofs for MATH 61CM, 61DM Week 1: basic logic, proof by contradiction, proof by induction Writing proofs for MATH 61CM, 61DM Week 1: basic logic, proof by contradiction, proof by induction written by Sarah Peluse, revised by Evangelie Zachos and Lisa Sauermann September 27, 2016 1 Introduction

More information

Mat 243 Exam 1 Review

Mat 243 Exam 1 Review OBJECTIVES (Review problems: on next page) 1.1 Distinguish between propositions and non-propositions. Know the truth tables (i.e., the definitions) of the logical operators,,,, and Write truth tables for

More information

1. Introduction to commutative rings and fields

1. Introduction to commutative rings and fields 1. Introduction to commutative rings and fields Very informally speaking, a commutative ring is a set in which we can add, subtract and multiply elements so that the usual laws hold. A field is a commutative

More information

Contribution of Problems

Contribution of Problems Exam topics 1. Basic structures: sets, lists, functions (a) Sets { }: write all elements, or define by condition (b) Set operations: A B, A B, A\B, A c (c) Lists ( ): Cartesian product A B (d) Functions

More information

Proofs. Introduction II. Notes. Notes. Notes. Slides by Christopher M. Bourke Instructor: Berthe Y. Choueiry. Fall 2007

Proofs. Introduction II. Notes. Notes. Notes. Slides by Christopher M. Bourke Instructor: Berthe Y. Choueiry. Fall 2007 Proofs Slides by Christopher M. Bourke Instructor: Berthe Y. Choueiry Fall 2007 Computer Science & Engineering 235 Introduction to Discrete Mathematics Sections 1.5, 1.6, and 1.7 of Rosen cse235@cse.unl.edu

More information

1.1 Statements and Compound Statements

1.1 Statements and Compound Statements Chapter 1 Propositional Logic 1.1 Statements and Compound Statements A statement or proposition is an assertion which is either true or false, though you may not know which. That is, a statement is something

More information

1 The Foundation: Logic and Proofs

1 The Foundation: Logic and Proofs 1 The Foundation: Logic and Proofs 1.1 Propositional Logic Propositions( ) a declarative sentence that is either true or false, but not both nor neither letters denoting propostions p, q, r, s, T: true

More information

Mathematical Reasoning. The Foundation of Algorithmics

Mathematical Reasoning. The Foundation of Algorithmics Mathematical Reasoning The Foundation of Algorithmics The Nature of Truth In mathematics, we deal with statements that are True or False This is known as The Law of the Excluded Middle Despite the fact

More information

Math 3336: Discrete Mathematics Practice Problems for Exam I

Math 3336: Discrete Mathematics Practice Problems for Exam I Math 3336: Discrete Mathematics Practice Problems for Exam I The upcoming exam on Tuesday, February 26, will cover the material in Chapter 1 and Chapter 2*. You will be provided with a sheet containing

More information

Prentice Hall Mathematics, Geometry 2009 Correlated to: Connecticut Mathematics Curriculum Framework Companion, 2005 (Grades 9-12 Core and Extended)

Prentice Hall Mathematics, Geometry 2009 Correlated to: Connecticut Mathematics Curriculum Framework Companion, 2005 (Grades 9-12 Core and Extended) Grades 9-12 CORE Algebraic Reasoning: Patterns And Functions GEOMETRY 2009 Patterns and functional relationships can be represented and analyzed using a variety of strategies, tools and technologies. 1.1

More information

Readings: Conjecture. Theorem. Rosen Section 1.5

Readings: Conjecture. Theorem. Rosen Section 1.5 Readings: Conjecture Theorem Lemma Lemma Step 1 Step 2 Step 3 : Step n-1 Step n a rule of inference an axiom a rule of inference Rosen Section 1.5 Provide justification of the steps used to show that a

More information

a + b = b + a and a b = b a. (a + b) + c = a + (b + c) and (a b) c = a (b c). a (b + c) = a b + a c and (a + b) c = a c + b c.

a + b = b + a and a b = b a. (a + b) + c = a + (b + c) and (a b) c = a (b c). a (b + c) = a b + a c and (a + b) c = a c + b c. Properties of the Integers The set of all integers is the set and the subset of Z given by Z = {, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, }, N = {0, 1, 2, 3, 4, }, is the set of nonnegative integers (also called

More information

Properties of the Integers

Properties of the Integers Properties of the Integers The set of all integers is the set and the subset of Z given by Z = {, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, }, N = {0, 1, 2, 3, 4, }, is the set of nonnegative integers (also called

More information

Problem 1: Suppose A, B, C and D are finite sets such that A B = C D and C = D. Prove or disprove: A = B.

Problem 1: Suppose A, B, C and D are finite sets such that A B = C D and C = D. Prove or disprove: A = B. Department of Computer Science University at Albany, State University of New York Solutions to Sample Discrete Mathematics Examination III (Spring 2007) Problem 1: Suppose A, B, C and D are finite sets

More information

Finding the Nucleoli of Large Cooperative Games: A Disproof with Counter-Example

Finding the Nucleoli of Large Cooperative Games: A Disproof with Counter-Example Finding the Nucleoli of Large Cooperative Games: A Disproof with Counter-Example Holger I. MEINHARDT arxiv:1603.00226v1 [cs.gt] 1 Mar 2016 March 6, 2016 Nguyen and Thomas (2016) claimed that they have

More information

Introduction to proofs. Niloufar Shafiei

Introduction to proofs. Niloufar Shafiei Introduction to proofs Niloufar Shafiei proofs Proofs are essential in mathematics and computer science. Some applications of proof methods Proving mathematical theorems Designing algorithms and proving

More information

3 The language of proof

3 The language of proof 3 The language of proof After working through this section, you should be able to: (a) understand what is asserted by various types of mathematical statements, in particular implications and equivalences;

More information

Discrete Mathematics

Discrete Mathematics Slides for Part IA CST 2015/16 Discrete Mathematics Prof Marcelo Fiore Marcelo.Fiore@cl.cam.ac.uk What are we up to? Learn to read and write, and also work with,

More information

2.2 Day 1: Date: Geometry

2.2 Day 1: Date: Geometry 2.2 Day 1: Date: Geometry A Conditional Statement is an statement. The is the part following if. The is the part following then. Ex 1). What are the hypothesis and the conclusion of the conditional statement?

More information

Math 13, Spring 2013, Lecture B: Midterm

Math 13, Spring 2013, Lecture B: Midterm Math 13, Spring 2013, Lecture B: Midterm Name Signature UCI ID # E-mail address Each numbered problem is worth 12 points, for a total of 84 points. Present your work, especially proofs, as clearly as possible.

More information

Introducing Proof 1. hsn.uk.net. Contents

Introducing Proof 1. hsn.uk.net. Contents Contents 1 1 Introduction 1 What is proof? 1 Statements, Definitions and Euler Diagrams 1 Statements 1 Definitions Our first proof Euler diagrams 4 3 Logical Connectives 5 Negation 6 Conjunction 7 Disjunction

More information

(4) Using results you have studied, show that if x, y are real numbers,

(4) Using results you have studied, show that if x, y are real numbers, Solutions to Homework 4, Math 310 (1) Give a direct proof to show that if a, b are integers which are squares of integers, then ab is the square of an integer. Proof. We show that if a, b are integers

More information

University of Ottawa CSI 2101 Midterm Test Instructor: Lucia Moura. February 9, :30 pm Duration: 1:50 hs. Closed book, no calculators

University of Ottawa CSI 2101 Midterm Test Instructor: Lucia Moura. February 9, :30 pm Duration: 1:50 hs. Closed book, no calculators University of Ottawa CSI 2101 Midterm Test Instructor: Lucia Moura February 9, 2010 11:30 pm Duration: 1:50 hs Closed book, no calculators Last name: First name: Student number: There are 5 questions and

More information

Chapter 2 Section 2.1: Proofs Proof Techniques. CS 130 Discrete Structures

Chapter 2 Section 2.1: Proofs Proof Techniques. CS 130 Discrete Structures Chapter 2 Section 2.1: Proofs Proof Techniques CS 130 Discrete Structures Some Terminologies Axioms: Statements that are always true. Example: Given two distinct points, there is exactly one line that

More information

Write the negation of each of the following propositions without using any form of the word not :

Write the negation of each of the following propositions without using any form of the word not : Write the negation of each of the following propositions without using any form of the word not : Today is Thursday Today is Monday or Tuesday or Wednesday or Friday or Saturday or Sunday 2 + 1 = 3 2+1

More information

Today. Proof using contrapositive. Compound Propositions. Manipulating Propositions. Tautology

Today. Proof using contrapositive. Compound Propositions. Manipulating Propositions. Tautology 1 Math/CSE 1019N: Discrete Mathematics for Computer Science Winter 2007 Suprakash Datta datta@cs.yorku.ca Office: CSEB 3043 Phone: 416-736-2100 ext 77875 Course page: http://www.cs.yorku.ca/course/1019

More information

MATH 271 Summer 2016 Practice problem solutions Week 1

MATH 271 Summer 2016 Practice problem solutions Week 1 Part I MATH 271 Summer 2016 Practice problem solutions Week 1 For each of the following statements, determine whether the statement is true or false. Prove the true statements. For the false statement,

More information

Proof by Contradiction

Proof by Contradiction Proof by Contradiction MAT231 Transition to Higher Mathematics Fall 2014 MAT231 (Transition to Higher Math) Proof by Contradiction Fall 2014 1 / 12 Outline 1 Proving Statements with Contradiction 2 Proving

More information

Example 1: Identifying the Parts of a Conditional Statement

Example 1: Identifying the Parts of a Conditional Statement "If p, then q" can also be written... If p, q q, if p p implies q p only if q Example 1: Identifying the Parts of a Conditional Statement Identify the hypothesis and conclusion of each conditional. A.

More information

Lecture 2. Logic Compound Statements Conditional Statements Valid & Invalid Arguments Digital Logic Circuits. Reading (Epp s textbook)

Lecture 2. Logic Compound Statements Conditional Statements Valid & Invalid Arguments Digital Logic Circuits. Reading (Epp s textbook) Lecture 2 Logic Compound Statements Conditional Statements Valid & Invalid Arguments Digital Logic Circuits Reading (Epp s textbook) 2.1-2.4 1 Logic Logic is a system based on statements. A statement (or

More information

1 Implication and induction

1 Implication and induction 1 Implication and induction This chapter is about various kinds of argument which are used in mathematical proofs. When you have completed it, you should know what is meant by implication and equivalence,

More information

CSE 20. Final Review. CSE 20: Final Review

CSE 20. Final Review. CSE 20: Final Review CSE 20 Final Review Final Review Representation of integers in base b Logic Proof systems: Direct Proof Proof by contradiction Contraposetive Sets Theory Functions Induction Final Review Representation

More information

x P(x) x P(x) CSE 311: Foundations of Computing announcements last time: quantifiers, review: logical Inference Fall 2013 Lecture 7: Proofs

x P(x) x P(x) CSE 311: Foundations of Computing announcements last time: quantifiers, review: logical Inference Fall 2013 Lecture 7: Proofs CSE 311: Foundations of Computing Fall 2013 Lecture 7: Proofs announcements Reading assignment Logical inference 1.6-1.7 7 th Edition 1.5-1.7 6 th Edition Homework #2 due today last time: quantifiers,

More information

CITS2211 Discrete Structures Proofs

CITS2211 Discrete Structures Proofs CITS2211 Discrete Structures Proofs Unit coordinator: Rachel Cardell-Oliver August 13, 2017 Highlights 1 Arguments vs Proofs. 2 Proof strategies 3 Famous proofs Reading Chapter 1: What is a proof? Mathematics

More information

Announcements For The Logic of Atomic Sentences Counterexamples & Formal Proofs. Logical Consequence & Validity The Definitions.

Announcements For The Logic of Atomic Sentences Counterexamples & Formal Proofs. Logical Consequence & Validity The Definitions. Announcements For 0906 The Logic of Atomic Sentences & William Starr 1 Complete survey for Logic section times (on Bb) Before Wednesday at midnight!! 2 HW1 & HW2 are due next Tuesday But you can start

More information

Steinhardt School of Culture, Education, and Human Development Department of Teaching and Learning. Mathematical Proof and Proving (MPP)

Steinhardt School of Culture, Education, and Human Development Department of Teaching and Learning. Mathematical Proof and Proving (MPP) Steinhardt School of Culture, Education, and Human Development Department of Teaching and Learning Terminology, Notations, Definitions, & Principles: Mathematical Proof and Proving (MPP) 1. A statement

More information

Midterm Exam Solution

Midterm Exam Solution Midterm Exam Solution Name PID Honor Code Pledge: I certify that I am aware of the Honor Code in effect in this course and observed the Honor Code in the completion of this exam. Signature Notes: 1. This

More information

software design & management Gachon University Chulyun Kim

software design & management Gachon University Chulyun Kim Gachon University Chulyun Kim 2 Outline Propositional Logic Propositional Equivalences Predicates and Quantifiers Nested Quantifiers Rules of Inference Introduction to Proofs 3 1.1 Propositional Logic

More information

Climbing an Infinite Ladder

Climbing an Infinite Ladder Section 5.1 Section Summary Mathematical Induction Examples of Proof by Mathematical Induction Mistaken Proofs by Mathematical Induction Guidelines for Proofs by Mathematical Induction Climbing an Infinite

More information

Direct Proof MAT231. Fall Transition to Higher Mathematics. MAT231 (Transition to Higher Math) Direct Proof Fall / 24

Direct Proof MAT231. Fall Transition to Higher Mathematics. MAT231 (Transition to Higher Math) Direct Proof Fall / 24 Direct Proof MAT231 Transition to Higher Mathematics Fall 2014 MAT231 (Transition to Higher Math) Direct Proof Fall 2014 1 / 24 Outline 1 Overview of Proof 2 Theorems 3 Definitions 4 Direct Proof 5 Using

More information