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Theorem dffn4 5474
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
StepHypRef Expression
1 eqid 2193 . . 3  |-  ran  F  =  ran  F
21biantru 302 . 2  |-  ( F  Fn  A  <->  ( F  Fn  A  /\  ran  F  =  ran  F ) )
3 df-fo 5252 . 2  |-  ( F : A -onto-> ran  F  <->  ( F  Fn  A  /\  ran  F  =  ran  F
) )
42, 3bitr4i 187 1  |-  ( F  Fn  A  <->  F : A -onto-> ran  F )
Colors of variables: wff set class
Syntax hints:    /\ wa 104    <-> wb 105    = wceq 1364   ran crn 4656    Fn wfn 5241   -onto->wfo 5244
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-gen 1460  ax-ext 2175
This theorem depends on definitions:  df-bi 117  df-cleq 2186  df-fo 5252
This theorem is referenced by:  funforn  5475  fimadmfo  5477  ffoss  5524  tposf2  6312  mapsn  6735  fifo  7029  quslem  12897  gausslemma2dlem1f1o  15124
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