Math 2.0

Mathematical logic and foundations Definition

Power set

Builds on Subset

Definition

Let AA be a set. The power set of AA is the set 𝒫(A)={S∣S⊆A}\mathcal{P}(A) = \{S \mid S \subseteq A\} of all subsets of AA.

Remarks

Other notations are 2A2^A and ℘(A)\wp(A). Example: 𝒫({1,2})={∅,{1},{2},{1,2}}\mathcal{P}(\{1, 2\}) = \{\varnothing, \{1\}, \{2\}, \{1, 2\}\}. A finite set with nn elements has a power set with 2n2^n elements. See cardinality of the power set. By Cantor's theorem, no set is in bijection with its power set.

Reading path

To understand this page from the ground up, read these 8 pages in order. The foundations come first.

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Each page uses the pages above it. The colour of the bar on a box shows how strong the evidence is, and the box also gives it as text. The list has the same pages.
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  1. Element definition
  2. Proposition concept
  3. Set definition
  4. Implication definition
  5. Predicate definition
  6. Universal quantifier definition
  7. Subset definition
  8. Power set definition

Where this leads

410 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Power_set, lead section
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