Theorem sn0top

Description: The singleton of the empty set is a topology. (Contributed by Stefan Allan, 3-Mar-2006) (Proof shortened by Mario Carneiro, 13-Aug-2015)

	Ref	Expression
Assertion	sn0top	⊢ { ∅ } ∈ Top

Proof

Step	Hyp	Ref	Expression
1		sn0topon	⊢ { ∅ } ∈ ( TopOn ‘ ∅ )
2	1	topontopi	⊢ { ∅ } ∈ Top