Complement of Empty Set is Universe

Theorem

The complement of the empty set is the universe:

$\map \complement \O = \mathbb U$

Proof

Substitute $\mathbb U$ for $S$ in $\relcomp S \O = S$ from Relative Complement of Empty Set.

$\blacksquare$

Also see

• Complement of Universe is Empty Set

Sources

• 1967: George McCarty: Topology: An Introduction with Application to Topological Groups ... (previous) ... (next): Chapter $\text{I}$: Sets and Functions: Exercise $\text{B i}$
• 1978: Thomas A. Whitelaw: An Introduction to Abstract Algebra ... (previous) ... (next): $\S 6.6$: Subsets
• 2008: Paul Halmos and Steven Givant: Introduction to Boolean Algebras ... (previous) ... (next): $\S 2$
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): algebra of sets: $\text {(viii)}$