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Theorem truni 4319
 Description: The union of a class of transitive sets is transitive. Exercise 5(a) of [Enderton] p. 73. (Contributed by Scott Fenton, 21-Feb-2011.) (Proof shortened by Mario Carneiro, 26-Apr-2014.)
Assertion
Ref Expression
truni
Distinct variable group:   ,

Proof of Theorem truni
StepHypRef Expression
1 triun 4318 . 2
2 uniiun 4146 . . 3
3 treq 4311 . . 3
42, 3ax-mp 5 . 2
51, 4sylibr 205 1
 Colors of variables: wff set class Syntax hints:   wi 4   wb 178   wceq 1653  wral 2707  cuni 4017  ciun 4095   wtr 4305 This theorem is referenced by:  dfon2lem1  25415 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1556  ax-5 1567  ax-17 1627  ax-9 1667  ax-8 1688  ax-6 1745  ax-7 1750  ax-11 1762  ax-12 1951  ax-ext 2419 This theorem depends on definitions:  df-bi 179  df-or 361  df-an 362  df-tru 1329  df-ex 1552  df-nf 1555  df-sb 1660  df-clab 2425  df-cleq 2431  df-clel 2434  df-nfc 2563  df-ral 2712  df-rex 2713  df-v 2960  df-in 3329  df-ss 3336  df-uni 4018  df-iun 4097  df-tr 4306
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