Theorem f1dom

Description: The domain of a one-to-one function is dominated by its codomain. (Contributed by NM, 19-Jun-1998)

	Ref	Expression
Hypothesis	f1dom.1	|- B e. _V
Assertion	f1dom	|- ( F : A -1-1-> B -> A ~<_ B )

Proof

Step	Hyp	Ref	Expression
1		f1dom.1	|- B e. _V
2		f1domg	|- ( B e. _V -> ( F : A -1-1-> B -> A ~<_ B ) )
3	1 2	ax-mp	|- ( F : A -1-1-> B -> A ~<_ B )