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Theorem trel 3941
Description: In a transitive class, the membership relation is transitive. (Contributed by NM, 19-Apr-1994.) (Proof shortened by Andrew Salmon, 9-Jul-2011.)
Assertion
Ref Expression
trel  |-  ( Tr  A  ->  ( ( B  e.  C  /\  C  e.  A )  ->  B  e.  A ) )

Proof of Theorem trel
Dummy variables  x  y are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 dftr2 3936 . 2  |-  ( Tr  A  <->  A. y A. x
( ( y  e.  x  /\  x  e.  A )  ->  y  e.  A ) )
2 eleq12 2152 . . . . . 6  |-  ( ( y  =  B  /\  x  =  C )  ->  ( y  e.  x  <->  B  e.  C ) )
3 eleq1 2150 . . . . . . 7  |-  ( x  =  C  ->  (
x  e.  A  <->  C  e.  A ) )
43adantl 271 . . . . . 6  |-  ( ( y  =  B  /\  x  =  C )  ->  ( x  e.  A  <->  C  e.  A ) )
52, 4anbi12d 457 . . . . 5  |-  ( ( y  =  B  /\  x  =  C )  ->  ( ( y  e.  x  /\  x  e.  A )  <->  ( B  e.  C  /\  C  e.  A ) ) )
6 eleq1 2150 . . . . . 6  |-  ( y  =  B  ->  (
y  e.  A  <->  B  e.  A ) )
76adantr 270 . . . . 5  |-  ( ( y  =  B  /\  x  =  C )  ->  ( y  e.  A  <->  B  e.  A ) )
85, 7imbi12d 232 . . . 4  |-  ( ( y  =  B  /\  x  =  C )  ->  ( ( ( y  e.  x  /\  x  e.  A )  ->  y  e.  A )  <->  ( ( B  e.  C  /\  C  e.  A )  ->  B  e.  A ) ) )
98spc2gv 2709 . . 3  |-  ( ( B  e.  C  /\  C  e.  A )  ->  ( A. y A. x ( ( y  e.  x  /\  x  e.  A )  ->  y  e.  A )  ->  (
( B  e.  C  /\  C  e.  A
)  ->  B  e.  A ) ) )
109pm2.43b 51 . 2  |-  ( A. y A. x ( ( y  e.  x  /\  x  e.  A )  ->  y  e.  A )  ->  ( ( B  e.  C  /\  C  e.  A )  ->  B  e.  A ) )
111, 10sylbi 119 1  |-  ( Tr  A  ->  ( ( B  e.  C  /\  C  e.  A )  ->  B  e.  A ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    /\ wa 102    <-> wb 103   A.wal 1287    = wceq 1289    e. wcel 1438   Tr wtr 3934
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 665  ax-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-10 1441  ax-11 1442  ax-i12 1443  ax-bndl 1444  ax-4 1445  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-i5r 1473  ax-ext 2070
This theorem depends on definitions:  df-bi 115  df-tru 1292  df-nf 1395  df-sb 1693  df-clab 2075  df-cleq 2081  df-clel 2084  df-nfc 2217  df-v 2621  df-in 3005  df-ss 3012  df-uni 3652  df-tr 3935
This theorem is referenced by:  trel3  3942  trintssmOLD  3951  ordtr1  4213  suctr  4246  trsuc  4247  ordn2lp  4359
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