Cartesian product of sets (A × B = {(a,b) : a ∈ A, b ∈ B}; |A × B| = |A| · |B|)

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A × B = {(a,b) : a ∈ A, b ∈ B}; |A × B| = |A| · |B|

What each symbol means

SymbolWhat it stands for
A, BSets
(a,b)Ordered pair
|A × B|Number of elements in the Cartesian product

When to use this

A × B ≠ B × A in general (ordered pairs). A × ∅ = ∅. A × (B ∪ C) = (A×B) ∪ (A×C).