Theorem f1dmOLD

Description: Obsolete version of f1dm as of 29-May-2024. (Contributed by NM, 8-Mar-2014) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	f1dmOLD	⊢ ( 𝐹 : 𝐴 –1-1→ 𝐵 → dom 𝐹 = 𝐴 )

Proof

Step	Hyp	Ref	Expression
1		f1fn	⊢ ( 𝐹 : 𝐴 –1-1→ 𝐵 → 𝐹 Fn 𝐴 )
2		fndm	⊢ ( 𝐹 Fn 𝐴 → dom 𝐹 = 𝐴 )
3	1 2	syl	⊢ ( 𝐹 : 𝐴 –1-1→ 𝐵 → dom 𝐹 = 𝐴 )