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Theorem uncom 3084
Description: Commutative law for union of classes. Exercise 6 of [TakeutiZaring] p. 17. (Contributed by NM, 25-Jun-1998.) (Proof shortened by Andrew Salmon, 26-Jun-2011.)
Assertion
Ref Expression
uncom  |-  ( A  u.  B )  =  ( B  u.  A
)

Proof of Theorem uncom
Dummy variable  x is distinct from all other variables.
StepHypRef Expression
1 orcom 647 . . 3  |-  ( ( x  e.  A  \/  x  e.  B )  <->  ( x  e.  B  \/  x  e.  A )
)
2 elun 3081 . . 3  |-  ( x  e.  ( B  u.  A )  <->  ( x  e.  B  \/  x  e.  A ) )
31, 2bitr4i 176 . 2  |-  ( ( x  e.  A  \/  x  e.  B )  <->  x  e.  ( B  u.  A ) )
43uneqri 3082 1  |-  ( A  u.  B )  =  ( B  u.  A
)
Colors of variables: wff set class
Syntax hints:    \/ wo 629    = wceq 1243    e. wcel 1393    u. cun 2912
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-io 630  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-10 1396  ax-11 1397  ax-i12 1398  ax-bndl 1399  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-tru 1246  df-nf 1350  df-sb 1646  df-clab 2027  df-cleq 2033  df-clel 2036  df-nfc 2167  df-v 2556  df-un 2919
This theorem is referenced by:  equncom  3085  uneq2  3088  un12  3098  un23  3099  ssun2  3104  unss2  3111  ssequn2  3113  undir  3184  dif32  3197  disjpss  3275  undif2ss  3296  uneqdifeqim  3305  prcom  3443  tpass  3463  prprc1  3475  difsnss  3507  suc0  4144  fvun2  5227  fmptpr  5342  fvsnun2  5348  fsnunfv  5350  omv2  6032  phplem2  6303  fzsuc2  8908  fseq1p1m1  8923
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