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Theorem unundir 4098
 Description: Union distributes over itself. (Contributed by NM, 17-Aug-2004.)
Assertion
Ref Expression
unundir ((𝐴𝐵) ∪ 𝐶) = ((𝐴𝐶) ∪ (𝐵𝐶))

Proof of Theorem unundir
StepHypRef Expression
1 unidm 4079 . . 3 (𝐶𝐶) = 𝐶
21uneq2i 4087 . 2 ((𝐴𝐵) ∪ (𝐶𝐶)) = ((𝐴𝐵) ∪ 𝐶)
3 un4 4096 . 2 ((𝐴𝐵) ∪ (𝐶𝐶)) = ((𝐴𝐶) ∪ (𝐵𝐶))
42, 3eqtr3i 2823 1 ((𝐴𝐵) ∪ 𝐶) = ((𝐴𝐶) ∪ (𝐵𝐶))
 Colors of variables: wff setvar class Syntax hints:   = wceq 1538   ∪ cun 3879 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-ext 2770 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-ex 1782  df-sb 2070  df-clab 2777  df-cleq 2791  df-clel 2870  df-v 3443  df-un 3886 This theorem is referenced by:  iocunico  40156
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