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What is A ∪ ∅?

Published in Set Theory 1 min read

A ∪ ∅ = A. In set theory, the union of any set A with the empty set (∅) is always the set A itself.

Here's a breakdown:

  • Union (∪): The union of two sets combines all the elements from both sets into a single set. Any element present in either set is included in the union.

  • Empty Set (∅): The empty set is a set that contains no elements. It is also known as the null set.

Therefore, when you take the union of set A with the empty set, you are essentially combining the elements of A with nothing. Since the empty set has no elements to contribute, the resulting set contains only the elements of A.

Example:

Let A = {1, 2, 3}

Then A ∪ ∅ = {1, 2, 3} ∪ {} = {1, 2, 3} = A

This principle is a fundamental identity law in set theory.