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Principle of Inclusion and Exclusion

The Principle of Inclusion and Exclusion (PIE) is a way to calculate the number of elements that satisfy at least one of several given properties. If there are two sets, the principle of inclusion and exclusion states

$|A \cup B| = |A|+|B| - |A\cap B|.$

If there are three sets, the principle of inclusion and exclusion states
$|A\cup B \cup C| = \\ |A| + |B| + |C| - |A \cap B| - |A \cap C| - |B \cap C| + |A \cap B \cap C|.$

Note by Arron Kau
2 years, 5 months ago