Theorem trv

Description: The universe is transitive. (Contributed by NM, 14-Sep-2003)

	Ref	Expression
Assertion	trv	⊢ Tr V

Proof

Step	Hyp	Ref	Expression
1		ssv	⊢ ∪ V ⊆ V
2		df-tr	⊢ ( Tr V ↔ ∪ V ⊆ V )
3	1 2	mpbir	⊢ Tr V