Theorem fndm

Description: The domain of a function. (Contributed by NM, 2-Aug-1994)

	Ref	Expression
Assertion	fndm	|- ( F Fn A -> dom F = A )

Proof

Step	Hyp	Ref	Expression
1		df-fn	|- ( F Fn A <-> ( Fun F /\ dom F = A ) )
2	1	simprbi	|- ( F Fn A -> dom F = A )