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Metamath Proof Explorer

Theorem fndmu

Description: A function has a unique domain. (Contributed by NM, 11-Aug-1994)

		Ref	Expression
	Assertion	fndmu	$⊢ (F Fn A \land F Fn B) \to A = B$

Step	Hyp	Ref	Expression
1		fndm	$⊢ F Fn A \to dom F = A$
2		fndm	$⊢ F Fn B \to dom F = B$
3	1 2	sylan9req	$⊢ (F Fn A \land F Fn B) \to A = B$