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Theorem dffo2 5397
Description: Alternate definition of an onto function. (Contributed by NM, 22-Mar-2006.)
Assertion
Ref Expression
dffo2 (𝐹:𝐴onto𝐵 ↔ (𝐹:𝐴𝐵 ∧ ran 𝐹 = 𝐵))

Proof of Theorem dffo2
StepHypRef Expression
1 fof 5393 . . 3 (𝐹:𝐴onto𝐵𝐹:𝐴𝐵)
2 forn 5396 . . 3 (𝐹:𝐴onto𝐵 → ran 𝐹 = 𝐵)
31, 2jca 304 . 2 (𝐹:𝐴onto𝐵 → (𝐹:𝐴𝐵 ∧ ran 𝐹 = 𝐵))
4 ffn 5320 . . 3 (𝐹:𝐴𝐵𝐹 Fn 𝐴)
5 df-fo 5177 . . . 4 (𝐹:𝐴onto𝐵 ↔ (𝐹 Fn 𝐴 ∧ ran 𝐹 = 𝐵))
65biimpri 132 . . 3 ((𝐹 Fn 𝐴 ∧ ran 𝐹 = 𝐵) → 𝐹:𝐴onto𝐵)
74, 6sylan 281 . 2 ((𝐹:𝐴𝐵 ∧ ran 𝐹 = 𝐵) → 𝐹:𝐴onto𝐵)
83, 7impbii 125 1 (𝐹:𝐴onto𝐵 ↔ (𝐹:𝐴𝐵 ∧ ran 𝐹 = 𝐵))
Colors of variables: wff set class
Syntax hints:  wa 103  wb 104   = wceq 1335  ran crn 4588   Fn wfn 5166  wf 5167  ontowfo 5169
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1427  ax-7 1428  ax-gen 1429  ax-ie1 1473  ax-ie2 1474  ax-8 1484  ax-11 1486  ax-4 1490  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2139
This theorem depends on definitions:  df-bi 116  df-nf 1441  df-sb 1743  df-clab 2144  df-cleq 2150  df-clel 2153  df-in 3108  df-ss 3115  df-f 5175  df-fo 5177
This theorem is referenced by:  foco  5403  dff1o5  5424  dffo3  5615  dffo4  5616  fo1stresm  6110  fo2ndresm  6111  fo2ndf  6175  1fv  10042
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