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Theorem infpssALT 7939
Description: A set with a denumerable subset has a proper subset equinumerous to it, proved without AC or Infinity. Unlike infpss 7843, it uses Replacement. (Contributed by Stefan O'Rear, 30-Oct-2014.) (Revised by Mario Carneiro, 16-May-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
infpssALT  |-  ( om  ~<_  A  ->  E. x
( x  C.  A  /\  x  ~~  A ) )
Distinct variable group:    x, A

Proof of Theorem infpssALT
StepHypRef Expression
1 ominf4 7938 . 2  |-  -.  om  e. FinIV
2 reldom 6869 . . . . 5  |-  Rel  ~<_
32brrelex2i 4730 . . . 4  |-  ( om  ~<_  A  ->  A  e.  _V )
4 isfin4 7923 . . . 4  |-  ( A  e.  _V  ->  ( A  e. FinIV 
<->  -.  E. x ( x  C.  A  /\  x  ~~  A ) ) )
53, 4syl 15 . . 3  |-  ( om  ~<_  A  ->  ( A  e. FinIV  <->  -. 
E. x ( x 
C.  A  /\  x  ~~  A ) ) )
6 domfin4 7937 . . . 4  |-  ( ( A  e. FinIV  /\  om  ~<_  A )  ->  om  e. FinIV )
76expcom 424 . . 3  |-  ( om  ~<_  A  ->  ( A  e. FinIV  ->  om  e. FinIV ) )
85, 7sylbird 226 . 2  |-  ( om  ~<_  A  ->  ( -.  E. x ( x  C.  A  /\  x  ~~  A
)  ->  om  e. FinIV )
)
91, 8mt3i 118 1  |-  ( om  ~<_  A  ->  E. x
( x  C.  A  /\  x  ~~  A ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 176    /\ wa 358   E.wex 1528    e. wcel 1684   _Vcvv 2788    C. wpss 3153   class class class wbr 4023   omcom 4656    ~~ cen 6860    ~<_ cdom 6861  FinIVcfin4 7906
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-13 1686  ax-14 1688  ax-6 1703  ax-7 1708  ax-11 1715  ax-12 1866  ax-ext 2264  ax-rep 4131  ax-sep 4141  ax-nul 4149  ax-pow 4188  ax-pr 4214  ax-un 4512
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-3or 935  df-3an 936  df-tru 1310  df-ex 1529  df-nf 1532  df-sb 1630  df-eu 2147  df-mo 2148  df-clab 2270  df-cleq 2276  df-clel 2279  df-nfc 2408  df-ne 2448  df-ral 2548  df-rex 2549  df-reu 2550  df-rab 2552  df-v 2790  df-sbc 2992  df-csb 3082  df-dif 3155  df-un 3157  df-in 3159  df-ss 3166  df-pss 3168  df-nul 3456  df-if 3566  df-pw 3627  df-sn 3646  df-pr 3647  df-tp 3648  df-op 3649  df-uni 3828  df-iun 3907  df-br 4024  df-opab 4078  df-mpt 4079  df-tr 4114  df-eprel 4305  df-id 4309  df-po 4314  df-so 4315  df-fr 4352  df-we 4354  df-ord 4395  df-on 4396  df-lim 4397  df-suc 4398  df-om 4657  df-xp 4695  df-rel 4696  df-cnv 4697  df-co 4698  df-dm 4699  df-rn 4700  df-res 4701  df-ima 4702  df-iota 5219  df-fun 5257  df-fn 5258  df-f 5259  df-f1 5260  df-fo 5261  df-f1o 5262  df-fv 5263  df-er 6660  df-en 6864  df-dom 6865  df-fin4 7913
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