Interactive Real Analysis - part of MathCS.org

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Let A and B be two sets. We say that A and B have the same cardinality if there is a bijection f from A to B. We write card(A) = card(B).

If there exists a function f from A to B that is injective (i.e. one-to-one) we say that card(A) card(B)

If there exists a function f from A to B that is surjective (i.e. onto) we say that card(A) card(B)

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