Comprehensive Set Theory Review with Dr. Cynthia Bailey Lee
Explore set sizes, builder notations, and practice exercises in this comprehensive review of discrete mathematics. Dr. Cynthia Bailey Lee guides you through key concepts for a solid understanding of set theory.
Comprehensive Set Theory Review with Dr. Cynthia Bailey Lee
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Presentation Transcript
Peer Instruction in Discrete Mathematics by Cynthia Leeis licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.Based on a work at http://peerinstruction4cs.org.Permissions beyond the scope of this license may be available at http://peerinstruction4cs.org. CSE 20 – Discrete Mathematics Dr. Cynthia Bailey Lee Dr. Shachar Lovett
Today’s Topics: • Set sizes • Set builder notation • Rapid-fire set-theory practice
Power set • Let A be a set of n elements (|A|=n) • How large is P(A) (the power-set of A)? • n • 2n • n2 • 2n • None/other/more than one
Cartesian product • |A|=n, |B|=m • How large is A x B ? • n+m • nm • n2 • m2 • None/other/more than one
Union • |A|=n, |B|=m • How large is A B ? • n+m • nm • n2 • m2 • None/other/more than one
Intersection • |A|=n, |B|=m • How large is A B ? • n+m • nm • At most n • At most m • None/other/more than one
Set builder notation • Example: Even • Our definition of Even is: • How can we write this as a set, rather than a definition applying to an individual n? • , or just • “|” is pronounced “such that”
Set builder notation • How could we write “the set of integers that are multiples of 12”? • Other/none/more than one
Ways of defining a set • Enumeration: • {1,2,3,4,5,6,7,8,9} • + very clear • - impractical for large sets • Incomplete enumeration (ellipses): • {1,2,3,…,98,99,100} • + takes up less space, can work for large or infinite sets • - not always clear • {2 3 5 7 11 13 …} What does this mean? What is the next element? • Set builder: • { n | <some criteria>} • + can be used for large or infinite sets, clearly sets forth rules for membership
Primes • Enumeration may not be clear: • {2 3 5 7 11 13 …} • How can we write the set Primes using set builder notation?
3. Rapid-fire set-theory practice Clickers ready!
Set Theory rapid-fire practice • (A and B are sets) • TRUE • FALSE In your discussion: If true, prove it! (quickly sketch out what the argument would be) If false, what are the counterexample A and B?
Set Theory rapid-fire practice • (A and B are sets) • TRUE • FALSE In your discussion: If true, prove it! (quickly sketch out what the argument would be) If false, what are the counterexample A and B?
Set Theory rapid-fire practice • (A is a set) • TRUE • FALSE In your discussion: If true, prove it! (quickly sketch out what the argument would be) If false, what are the counterexample A and B?