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Theorem dffn4 5275
Description: A function maps onto its range. (Contributed by set.mm contributors, 10-May-1998.)
Assertion
Ref Expression
dffn4

Proof of Theorem dffn4
StepHypRef Expression
1 eqid 2353 . . 3
21biantru 491 . 2
3 df-fo 4793 . 2
42, 3bitr4i 243 1
Colors of variables: wff setvar class
Syntax hints:   wb 176   wa 358   wceq 1642   crn 4773   wfn 4776  wfo 4779
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-ext 2334
This theorem depends on definitions:  df-bi 177  df-an 360  df-cleq 2346  df-fo 4793
This theorem is referenced by:  funforn  5276  ffoss  5314  mapsn  6026
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