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Exercise 277Logic, sets and proofs › Sets and mapsHigh schoolAdded 3 Nov 2026

Basic set operations

#sets#union#intersection#complement

Statement

Let A={1,2,3,4}A=\{1,2,3,4\}, B={3,4,5,6}B=\{3,4,5,6\} and the universe be E={1,…,8}E=\{1,\ldots,8\}. Compute A∪BA\cup B, A∩BA\cap B, A∖BA\setminus B, A△BA\triangle B, and A‾\overline{A}.

Hint

Union = all elements in at least one set; intersection = common elements; complement = elements of EE not in AA.

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Solution

Union. A∪B={1,2,3,4,5,6}A\cup B=\{1,2,3,4,5,6\}.

Intersection. A∩B={3,4}A\cap B=\{3,4\}.

Difference. A∖B={1,2}A\setminus B=\{1,2\}.

Symmetric difference. A△B=(A∖B)∪(B∖A)={1,2,5,6}A\triangle B=(A\setminus B)\cup(B\setminus A)=\{1,2,5,6\}.

Complement. A‾=E∖A={5,6,7,8}\overline{A}=E\setminus A=\{5,6,7,8\}.