Theorem dffn4 5132

Description: A function maps onto its range. (Contributed by NM, 10-May-1998.)

Assertion

Ref	Expression
dffn4	⊢ (𝐹 Fn 𝐴 ↔ 𝐹:𝐴–onto→ran 𝐹)

Proof of Theorem dffn4

Step	Hyp	Ref	Expression
1		eqid 2081	. . 3 ⊢ ran 𝐹 = ran 𝐹
2	1	biantru 296	. 2 ⊢ (𝐹 Fn 𝐴 ↔ (𝐹 Fn 𝐴 ∧ ran 𝐹 = ran 𝐹))
3		df-fo 4928	. 2 ⊢ (𝐹:𝐴–onto→ran 𝐹 ↔ (𝐹 Fn 𝐴 ∧ ran 𝐹 = ran 𝐹))
4	2, 3	bitr4i 185	1 ⊢ (𝐹 Fn 𝐴 ↔ 𝐹:𝐴–onto→ran 𝐹)

Syntax hints:   ∧ wa 102   ↔ wb 103   = wceq 1284  ran crn 4364   Fn wfn 4917  –onto→wfo 4920

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-gen 1378  ax-ext 2063

This theorem depends on definitions:  df-bi 115  df-cleq 2074  df-fo 4928

This theorem is referenced by:  funforn  5133  ffoss  5178  tposf2  5906