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Theorem dfss3 2935
Description: Alternate definition of subclass relationship. (Contributed by NM, 14-Oct-1999.)
Assertion
Ref Expression
dfss3  |-  ( A 
C_  B  <->  A. x  e.  A  x  e.  B )
Distinct variable groups:    x, A    x, B

Proof of Theorem dfss3
StepHypRef Expression
1 dfss2 2934 . 2  |-  ( A 
C_  B  <->  A. x
( x  e.  A  ->  x  e.  B ) )
2 df-ral 2311 . 2  |-  ( A. x  e.  A  x  e.  B  <->  A. x ( x  e.  A  ->  x  e.  B ) )
31, 2bitr4i 176 1  |-  ( A 
C_  B  <->  A. x  e.  A  x  e.  B )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 98   A.wal 1241    e. wcel 1393   A.wral 2306    C_ wss 2917
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-11 1397  ax-4 1400  ax-17 1419  ax-i9 1423  ax-ial 1427  ax-i5r 1428  ax-ext 2022
This theorem depends on definitions:  df-bi 110  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-ral 2311  df-in 2924  df-ss 2931
This theorem is referenced by:  ssrab  3018  eqsnm  3526  uni0b  3605  uni0c  3606  ssint  3631  ssiinf  3706  sspwuni  3739  dftr3  3858  tfis  4306  rninxp  4764  fnres  5015  eqfnfv3  5267  funimass3  5283  ffvresb  5328  tfrlemibxssdm  5941  bdss  9984
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