notebook/notes/combinatorics/index.md

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Combinatorics Obsidian::STEM combinatorics set
combinatorics
set

Overview

The additive principle states that two finite and disjoint sets A and B satisfy |A \cup B| = |A| + |B|

The multiplicative principle states that two finite sets A and B satisfy |A \times B| = |A| \cdot |B|

%%ANKI Basic What does the additive principle state? Back: Given finite and disjoint sets A and B, |A \cup B| = |A| + |B|. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic What does the multiplicative principle state? Back: Given finite sets A and B, |A \times B| = |A| \cdot |B|. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic The additive property applies to sets exhibiting what two properties? Back: Finiteness and disjointedness. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic The multiplicative property applies to sets exhibiting what property? Back: Finiteness. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Cloze The additive principle is to {\cup} whereas the multiplicative principle is to {\times}. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic If A is finite, how is A \times B rewritten as |A| disjoint sets? Back: Given A = \{a_1, \ldots, a_n\}, (\{a_1\} \times B) \cup \cdots \cup (\{a_n\} \times B). Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic If B is finite, how is A \times B rewritten as |B| disjoint sets? Back: Given B = \{b_1, \ldots, b_n\}, (A \times \{b_1\}) \cup \cdots \cup (A \times \{b_n\}). Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic How do we denote A and B are disjoint using standard set notation? Back: A \cap B = \varnothing Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic How is the cartesian product A \times B defined? Back: A \times B = \{\langle x, y \rangle : x \in A \land y \in B\} Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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References