– If ( A = a,b ), ( B = 1,2,3 ), list ( A \times B ) and ( B \times A ).
6.1: (a) Yes; (b) No (1 maps to two values); (c) No (3 has no image). Chapter 7: Cardinality and Infinity Focus: Finite vs infinite, countable vs uncountable, Cantor’s theorem.
– Prove that the set of even natural numbers is countably infinite.
4.1: Let ( x \in (A \cup B)^c ) → ( x \notin A \cup B ) → ( x \notin A ) and ( x \notin B ) → ( x \in A^c \cap B^c ). Reverse similarly. 4.2: (description of shaded regions: intersection of A and B, plus parts of C outside A). Chapter 5: Ordered Pairs and Cartesian Products Focus: Ordered pairs, product of sets, relations. set theory exercises and solutions pdf
– Explain Russell’s paradox using the set ( R = x \mid x \notin x ). Why is this not a set in ZFC?
– True or false: (a) ( \emptyset \subseteq \emptyset ) (b) ( \emptyset \in \emptyset ) (c) ( \emptyset \subseteq \emptyset ) (d) ( \emptyset \in \emptyset )
– Show that ( \mathbbR ) is uncountable (sketch Cantor’s diagonal argument). – If ( A = a,b ), (
8.1: If ( R \in R ) → ( R \notin R ) by definition; if ( R \notin R ) → ( R \in R ). Contradiction → ( R ) cannot be a set; it’s a proper class. Epilogue: The Archive Opens Having solved the exercises, the apprentices returned to Professor Caelus. He smiled and handed them a single golden key—not to a building, but to the understanding that set theory is the foundation upon which all of modern mathematics rests.
3.1: (a) 1,2,3,4,5,6,7,8, (b) 4,5, (c) 1,2,3, (d) 1,2,3,9,10. Chapter 4: Venn Diagrams and Logical Arguments Focus: Visualizing sets, proving set identities, De Morgan’s laws.
7.1: Map ( f(n) = 2n ) from ( \mathbbN ) to evens is bijective. 7.2: Assume ( (0,1) ) countable → list decimals → construct new decimal differing at nth place → contradiction. Chapter 8: Paradoxes and Advanced Topics Focus: Russell’s paradox, axiom of choice, Zorn’s lemma (optional). – Prove that the set of even natural
– List the elements of: ( A = x \in \mathbbZ \mid -3 < x \leq 4 )
2.1: ( \emptyset, 1, 2, 3, 1,2, 1,3, 2,3, 1,2,3 ) → ( 2^3 = 8 ) subsets. 2.2: (a) T, (b) F (empty set has no elements), (c) T, (d) T. Chapter 3: Set Operations Focus: Union, intersection, complement, difference, symmetric difference.