Solution Manual for A Transition to Advanced Mathematics, 7th Edition

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CONTENTS Chapter 1.1 Propositions and Connectives 1 1.2 Conditionals and Biconditionals 6 1.3 Quantifiers 13 1.4 Basic Proof Methods I 17 1.5 Basic Proof Methods II 22 1.6 Proofs Involving Quantifiers 26 1.7 Additional Examples of Proofs 29 Chapter 2.1 Basic Concepts of Set Theory 38 2.2 Set Operations 40 2.3 Extended Set Operations and Indexed Families of Sets 2.4 Mathematical Induction 49 2.5 Equivalent Forms of Induction 59 2.6 Principles of Counting 62 Chapter 3.1 Cartesian Products and Relations 3.2 Equivalence Relations 70 3.3 Partitions 75 3.4 Ordering Relations 78 3.5 Graphs 82 46 67 Chapter 4.1 Functions as Relations 85 4.2 Constructions of Functions 88 4.3 Functions That Are Onto; One-to-One Functions 92 4.4 One-to-One Correspondences and Inverse Functions 95 4.5 Images of Sets 199 4.6 Sequences 102 Chapter 5.1 Equivalent Sets; Finite Sets 105 5.2 Infinite Sets 108 5.3 Countable Sets 111 5.4 The Ordering of Cardinal Numbers 114 5.5 Comparability of Cardinal Numbers and the Axiom of Choice Chapter 6.1 Algebraic Structures 119 6.2 Groups 122 6.3 Subgroups 126 6.4 Operation Preserving Maps 6.5 Rings and Fields 131 128 Chapter 7.1 Completeness of the Real Numbers 133 7.2 The Heine-Borel Theorem 136 7.3 The Bolzano-Weierstrass Theorem 139 7.4 The Bounded Monotone Sequence Theorem 7.5 Equivalents of Completeness 143 140 117 1 Logic and Proofs 1.1 Propositions and Connectives 1. (a) true (e) false (b) false (f) false (c) true (g) false (d) false (h) false 2. (a) Not a proposition (b) False proposition (c) Not a proposition. It would be a proposition if a value for x had been assigned. (d) Not a proposition. It would be a proposition if values for x and y had been assigned. (e) False proposition (f) True proposition (g) False proposition (h) True proposition (i) False proposition (j) Not a proposition. It is neither true nor false. 3. (a) (b) (c) (d) (e) (f) P T F โˆผP F T Pโˆง โˆผ P T F P T F โˆผP F T Pโˆจ โˆผ P T T P T F T F Q T T F F โˆผQ F F T T Pโˆง โˆผ Q F F T F P T F T F Q T T F F โˆผQ F F T T Qโˆจ โˆผ Q T T T T P T F T F Q T T F F โˆผQ F F T T P โˆงQ T F F F P T F T F Q T T F F P โˆงQ T F F F P โˆง (Qโˆจ โˆผ Q) T F T F (P โˆง Q)โˆจ โˆผ Q T F T T โˆผ (P โˆง Q) F T T T 1 1 LOGIC AND PROOFS (g) (h) (i) (j) 4. 2 โˆผQ F F T T F F T T Pโˆจ โˆผ Q T F T T T F T T (P โˆจ โˆผ Q) โˆง R T F T T F F F F P T F T F T F T F Q T T F F T T F F R T T T T F F F F P T F T F Q T T F F โˆผP F T F T โˆผQ F F T T โˆผ Pโˆง โˆผ Q F F F T P T F T F T F T F Q T T F F T T F F R T T T T F F F F QโˆจR T T T T T T F F P โˆง (Q โˆจ R) T F T F T F F F P T F T F T F T F Q T T F F T T F F R T T T T F F F F P โˆงQ T F F F T F F F P โˆงR T F T F F F F F (a) false (e) false (i) true (b) true (f) false (j) true (P โˆง Q) โˆจ (P โˆง R) T F T F T F F F (c) true (g) false (k) false (d) true (h) false (1) false 5. (a) No solution. (b) P Q P โˆจQ QโˆจP T T T T F T T T T F T T F F F F Since the third and fourth columns are the same, the propositions are equivalent. 1 LOGIC AND PROOFS (c) (d) (e) (f) (g) 3 P Q P โˆงQ QโˆงP T T T T F T F F T F F F F F F F Since the third and fourth columns are the same, the propositions are equivalent. P Q R Q โˆจ R P โˆจ (Q โˆจ R) P โˆจ Q (P โˆจ Q) โˆจ R T T T T T T T F T T T T T T T F T T T T T F F T T T F T T T F T T T T F T F T T T T T F F F T T T F F F F F F F Since the ๏ฌfth and seventh columns are the same, the propositions are equivalent. P Q R Q โˆง R P โˆง (Q โˆง R) P โˆง Q (P โˆง Q) โˆง R T T T T T T T F T T T F F F T F T F F F F F F T F F F F T T F F F T F F T F F F F F T F F F F F F F F F F F F F Since the ๏ฌfth and seventh columns are the same, the propositions are equivalent. P Q R Q โˆจ R P โˆง (Q โˆจ R) P โˆง Q P โˆง R (P โˆง Q) โˆจ (P โˆง R) T T T T T T T T F T T T F F F F T F T T T F T T F F T T F F F F T T F T T T F T F T F T F F F F T F F F F F F F F F F F F F F F Since the ๏ฌfth and eighth columns are the same, the propositions are equivalent. P T F T F T F T F Q T T F F T T F F R T T T T F F F F QโˆงR T T F F F F F F P โˆจ (Q โˆง R) T T T F T F T F P โˆจQ T T T F T T T F P โˆจR T T T T T F T F (P โˆจ Q) โˆง (P โˆจ R) T T T F T F T F 1 LOGIC AND PROOFS 4 Since the ๏ฌfth and eighth columns are the same, the propositions are equivalent. (h) No solution. (i) P Q P โˆจ Q โˆผ (P โˆจ Q) โˆผ P โˆผ Q โˆผ P โˆง โˆผ Q T T T F F F F F T T F T F F T F T F F T F F F F T T T T Since the fourth and eighth columns are the same, the propositions are equivalent. 6. (a) equivalent (c) equivalent (e) equivalent (g) not equivalent (b) equivalent (d) equivalent (f) not equivalent (h) not equivalent 7. (a) โˆผ P , true (c) P Q, true (b) P โˆง Q, true (d) P โˆจ Q โˆจ R, true 8. (a) Since P is equivalent to Q, P has the same truth table as Q. Therefore, Q has the same truth table as P , so Q is equivalent to P . (b) Since P is equivalent to Q, P and Q have the same truth table. Since Q is equivalent to R, Q and R have the same truth table. Thus, P and R have the same truth table so P is equivalent to R. (c) Since P is equivalent to Q, P and Q have the same truth table. That is, the truth table for P has value true on exactly the same lines that the truth table for Q has value true. Therefore the truth table for โˆผ Q has value false on exactly the same lines that the truth table for โˆผ P has the value false. Thus โˆผ Q and โˆผ P have the same truth table. 9. (a) (P โˆง Q) โˆจ (โˆผ P โˆง โˆผ Q) is neither. P T F T F Q T T F F โˆผP F T F T โˆผQ F F T T P โˆงQ T F F F โˆผ Pโˆง โˆผ Q F F F T (P โˆง Q) โˆจ (โˆผ P โˆง โˆผ Q) T F F T (b) โˆผ (P โˆง โˆผ P ) is a tautology. P T F โˆผP F T Pโˆง โˆผ P F F โˆผ (P โˆง โˆผ P ) T T (c) (P โˆง Q) โˆจ (โˆผ P โˆจ โˆผ Q) is a tautology. P T F T F Q T T F F โˆผP F T F T โˆผQ F F T T P โˆงQ T F F F โˆผ Pโˆจ โˆผ Q F T T T (P โˆง Q) โˆจ (โˆผ P โˆจ โˆผ Q) T T T T (d) (A โˆง B) โˆจ (Aโˆง โˆผ B) โˆจ (โˆผ A โˆง B) โˆจ (โˆผ Aโˆง โˆผ B) is a tautology. 1 LOGIC AND PROOFS A T F T F B T T F F โˆผA F T F T โˆผB F F T T 5 AโˆงB T F F F Aโˆง โˆผ B F F T F โˆผAโˆงB F T F F โˆผ Aโˆง โˆผ B F F F T (A โˆง B) โˆจ (Aโˆง โˆผ B)โˆจ (โˆผ A โˆง B) โˆจ (โˆผ Aโˆง โˆผ B) T T T T (e) (Qโˆง โˆผ P )โˆง โˆผ (P โˆง R) is neither. P T F T F T F T F Q T T F F T T F F R T T T T F F F F โˆผP F T F T F T F T Qโˆง โˆผ P F T F F F T F F P โˆงR T F T F F F F F โˆผ (P โˆง R) F T F T T T T T (Qโˆง โˆผ P )โˆง โˆผ (P โˆง R) F T F F F T F F (f) P โˆจ [(โˆผ Q โˆง P ) โˆง (R โˆจ Q)] is neither. P T F T F T F T F 10. Q T T F F T T F F R T T T T F F F F โˆผQ F F T T F F T T โˆผQโˆงP F F T F F F T F (a) contradiction (c) tautology RโˆจQ T T T T T T F F [(โˆผ Q โˆง P ) โˆง (R โˆจ Q)] F F T F F F F F P โˆจ [(โˆผ Q โˆง P ) โˆง (R โˆจ Q)] T F T F T F T F (b) tautology (d) tautology 11. (a) x is not a positive integer. (b) Cleveland will lose the ๏ฌrst game and the second game. Or, Cleveland will lose both games. (c) 5 < 3 (d) 641,371 is not composite. Or 641,371 is prime. (e) Roses are not red or violets are not blue. (f) T is bounded and T is not compact. (g) M is not odd or M is not one-to-one. (h) The function.f does not have a positive ๏ฌrst derivative at x or does not have a positive second derivative at x. (i) The function g does not have a relative maximum at x = 2 (deleted comma) and does not have a relative maximum at x = 4, or else g does not have a relative minimum at x = 3. (j) z 4) โˆจ (n > 10) (i) (x is Cauchy) โ‡’ (x is convergent) (j) (limxโ†’x0 f (x) = f (x0 )) โ‡’ (f is continuous at x0 ) (k) [(f is di๏ฌ€erentiable at x0 ) โˆง (f is strictly increasing at x0 )] โ‡’ (f (x0 )) 11. (a) Let S be โ€œI go to the storeโ€ and R be โ€œIt rains.โ€ The preferred translation: is โˆผ S โ‡’ R (or, equivalently, โˆผ R โ‡’ S). This could be read as โ€œIf it doesnโ€™t rain, then I go to the store.โ€ The speaker might mean โ€œI go to the store if and only if it doesnโ€™t rain (S โ‡’โˆผ R) or possibly โ€œIf it rains, then I donโ€™t go to the storeโ€ (R โ‡’โˆผ S). (b) There are three nonequivalent ways to translate the sentence, using the symbols D: โ€œThe Dolphins make the playo๏ฌ€sโ€ and B: โ€œThe Bears win all the rest of their games.โ€ The ๏ฌrst translation is preferred, but the speaker may have intended any of the three. โˆผ B โ‡’โˆผ D or, equivalently, D โ‡’ B โˆผ D โ‡’โˆผ B or, equivalently, B โ‡’ D โˆผ B โ‡”โˆผ D or, equivalently, B โ‡” D (c) Let G be โ€œYou can go to the gameโ€ and H be โ€œYou do your homework ๏ฌrst.โ€ It is most likely that a student and parent both interpret this statement as a biconditional, G โ‡” H. (d) Let W be โ€œYou win the lotteryโ€ and T be โ€œYou buy a ticket.โ€ Of the three common interpretations for the word โ€œunless,โ€ only the form โˆผ T โ‡’โˆผ W (or, equivalently, W โ‡’ T ) makes sense here. 12. (a) (b) P Q R P โˆจ Q (P โˆจ Q) โ‡’ R โˆผ P โˆง โˆผ Q โˆผ R โ‡’ (โˆผ P โˆง โˆผ Q) T T T T T F T F T T T T F T T F T T T F T F F T F T T T T T F T F F F F T F T F F F T F F T F F F F F F F T T T Since the ๏ฌfth and seventh columns are the same, (P โˆจ Q) โ‡’ R and โˆผ R โ‡’ (โˆผ P โˆง โˆผ Q) are equivalent. P T F T F T F T F Q T T F F T T F F R T T T T F F F F P โˆงQ T F F F T F F F (P โˆง Q) โ‡’ R T T T T F T T T โˆผQ F F T T F F T T โˆผR F F F F T T T T Pโˆง โˆผ R F F F F T F T F (P โˆง โˆผ R) โ‡’โˆผ Q T T T T F T T T Since the ๏ฌfth and ninth columns are the same, the propositions (P โˆง Q) โ‡’ R and (P โˆง โˆผ R) โ‡’โˆผ Q are equivalent. 1 LOGIC AND PROOFS (c) (d) (e) (f) 12 P Q R Q โˆง R P โ‡’ (Q โˆง R) โˆผ Qโˆจ โˆผ R (โˆผ Qโˆจ โˆผ R) โ‡’โˆผ P T T T T T F T F T T T T F T T F T F F T F F F T F T T T T T F F F T F F T F F T T T T F F F F T F F F F F T T T Since the ๏ฌfth and seventh columns are the same, the propositions P โ‡’ (Q โˆง R) and (โˆผ Qโˆจ โˆผ R) โ‡’โˆผ P are equivalent. P Q R Q โˆจ R P โ‡’ (Q โˆจ R) P โˆง โˆผ R (P โˆง โˆผ R) โ‡’ Q T T T T T F T F T T T T F T T F T T T F T F F T T T F T T T F T T T T F T F T T F T T F F F F T F F F F F T F T Since the ๏ฌfth and seventh columns are the same, the propositions P โ‡’ (Q โˆจ R) and (P โˆง โˆผ R) โ‡’ Q are equivalent. P Q R P โ‡’ Q (P โ‡’ Q) โ‡’ R P โˆง โˆผ Q (P โˆง โˆผ Q) โˆจ R T T T T T F T F T T T T F T T F T F T T T F F T T T F T T T F T F F F F T F T F F F T F F F T T T F F F T F F F Since the ๏ฌfth and seventh columns are the same, the propositions (P โ‡’ Q) โ‡’ R and (P โˆง โˆผ Q) โˆจ R are equivalent. P Q P โ‡” Q โˆผ P โˆจ Q โˆผ Q โˆจ P (โˆผ P โˆจ Q) โˆง (โˆผ Q โˆจ P ) T T T T T T F T F T F F T F F F T F F F T T T T Since the third and sixth columns are the same, the propositions P โ‡” Q and (โˆผ P โˆจ Q) โˆง (โˆผ Q โˆจ P ) are equivalent. 13. (a) If 6 is an even integer, then 7 is an odd integer. (b) If 6 is an odd integer, then 7 is an odd integer. (c) This is not possible. (d) If 6 is an even integer, then 7 is an even integer. (Any true conditional statement will work here.) 14. (a) If 7 is an odd integer, then 6 is an odd integer. (b) This is not possible. 1 LOGIC AND PROOFS 13 (c) This is not possible. (d) If 7 is an odd integer, then 6 is an odd integer. (Any false conditional statement will work here.) 15. (a) Converse: If f (x0 ) = 0, then f has a relative minimum at x0 and is di๏ฌ€erentiable at x0 . False: f (x) = x3 has ๏ฌrst derivative 0 but no minimum at x0 = 0. Contrapositive: If f (x0 ) = 0, then f either has no relative minimum at x0 or is not di๏ฌ€erentiable at x0 . True. (b) Converse: If n = 2 or n is odd, then n is prime. False: 9 is odd but not prime. Contrapositive: If n is even and not equal to 2, then n is not prime. True. (c) Converse: If x is irrational, then x is real and not rational. True Contrapositive: If x is not irrational, then x is not real or x is rational. True (d) Converse: If |x| = 1, then x = 1 or x = โˆ’1. True. Contrapositive: If |x| = 1, then x = 1 and x = โˆ’1. True. 16. (a) tautology (d) neither (g) contradiction (j) neither 17. (a) (b) tautology (e) tautology (h) tautology (k) tautology (c) contradiction (f) neither (i) contradiction (l) neither P Q P โ‡’ Q โˆผ P โˆผ Q โˆผ P โ‡’โˆผ Q T T T F F T F T T T F F T F F F T T F F T T T T Comparison of the third and sixth columns of the truth table shows that P โ‡’ Q and โˆผ P โ‡’โˆผ Q are not equivalent. (b) We see from the truth table in part (a) that both propositions P โ‡’ Q and โˆผ P โ‡’โˆผ Q are true only when P and Q have the same truth value. (c) The converse of P โ‡’ Q is Q โ‡’ P . The contrapositive of the inverse of P โ‡’ Q is โˆผโˆผ Q โ‡’โˆผโˆผ P , so the converse and the contrapositive of the inverse are equivalent. The inverse of the contrapositive of P โ‡’ Q is also โˆผโˆผ Q โ‡’โˆผโˆผ P , so it too is equivalent to the converse. 1.3 Quanti๏ฌers 1. (a) โˆผ (โˆ€x)(x is preciousโ‡’ x is beautiful) or (โˆƒ x)(x is precious and x is not beautiful) (b) (โˆ€x)(x is preciousโ‡’ x is not beautiful) (c) (โˆƒ x)(x is isoscelesโˆงx is a right triangle) (d) (โˆ€x)(x is a right triangleโ‡’ x is not isosceles) or โˆผ (โˆƒ x)(x is a right triangleโˆงx is isosceles) (e) (โˆ€x)(x is honest)โˆจ โˆผ (โˆƒ x)(x is honest) (f) (โˆƒ x)(x is honest) โˆง (โˆƒ x)(x is not honest) (g) (โˆ€x)(x = 0 โ‡’ (x > 0 โˆจ x โˆ’4 โˆจ x โˆ’4 โˆจ x < 6)

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