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Theorem coundi 5008
 Description: Class composition distributes over union. (Contributed by NM, 21-Dec-2008.) (Proof shortened by Andrew Salmon, 27-Aug-2011.)
Assertion
Ref Expression
coundi (𝐴 ∘ (𝐵𝐶)) = ((𝐴𝐵) ∪ (𝐴𝐶))

Proof of Theorem coundi
Dummy variables 𝑥 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 unopab 3975 . . 3 ({⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦)} ∪ {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)}) = {⟨𝑥, 𝑦⟩ ∣ (∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦) ∨ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦))}
2 brun 3947 . . . . . . . 8 (𝑥(𝐵𝐶)𝑧 ↔ (𝑥𝐵𝑧𝑥𝐶𝑧))
32anbi1i 451 . . . . . . 7 ((𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦) ↔ ((𝑥𝐵𝑧𝑥𝐶𝑧) ∧ 𝑧𝐴𝑦))
4 andir 791 . . . . . . 7 (((𝑥𝐵𝑧𝑥𝐶𝑧) ∧ 𝑧𝐴𝑦) ↔ ((𝑥𝐵𝑧𝑧𝐴𝑦) ∨ (𝑥𝐶𝑧𝑧𝐴𝑦)))
53, 4bitri 183 . . . . . 6 ((𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦) ↔ ((𝑥𝐵𝑧𝑧𝐴𝑦) ∨ (𝑥𝐶𝑧𝑧𝐴𝑦)))
65exbii 1567 . . . . 5 (∃𝑧(𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦) ↔ ∃𝑧((𝑥𝐵𝑧𝑧𝐴𝑦) ∨ (𝑥𝐶𝑧𝑧𝐴𝑦)))
7 19.43 1590 . . . . 5 (∃𝑧((𝑥𝐵𝑧𝑧𝐴𝑦) ∨ (𝑥𝐶𝑧𝑧𝐴𝑦)) ↔ (∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦) ∨ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)))
86, 7bitr2i 184 . . . 4 ((∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦) ∨ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)) ↔ ∃𝑧(𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦))
98opabbii 3963 . . 3 {⟨𝑥, 𝑦⟩ ∣ (∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦) ∨ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦))} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦)}
101, 9eqtri 2136 . 2 ({⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦)} ∪ {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)}) = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦)}
11 df-co 4516 . . 3 (𝐴𝐵) = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦)}
12 df-co 4516 . . 3 (𝐴𝐶) = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)}
1311, 12uneq12i 3196 . 2 ((𝐴𝐵) ∪ (𝐴𝐶)) = ({⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐵𝑧𝑧𝐴𝑦)} ∪ {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥𝐶𝑧𝑧𝐴𝑦)})
14 df-co 4516 . 2 (𝐴 ∘ (𝐵𝐶)) = {⟨𝑥, 𝑦⟩ ∣ ∃𝑧(𝑥(𝐵𝐶)𝑧𝑧𝐴𝑦)}
1510, 13, 143eqtr4ri 2147 1 (𝐴 ∘ (𝐵𝐶)) = ((𝐴𝐵) ∪ (𝐴𝐶))
 Colors of variables: wff set class Syntax hints:   ∧ wa 103   ∨ wo 680   = wceq 1314  ∃wex 1451   ∪ cun 3037   class class class wbr 3897  {copab 3956   ∘ ccom 4511 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 681  ax-5 1406  ax-7 1407  ax-gen 1408  ax-ie1 1452  ax-ie2 1453  ax-8 1465  ax-10 1466  ax-11 1467  ax-i12 1468  ax-bndl 1469  ax-4 1470  ax-17 1489  ax-i9 1493  ax-ial 1497  ax-i5r 1498  ax-ext 2097 This theorem depends on definitions:  df-bi 116  df-tru 1317  df-nf 1420  df-sb 1719  df-clab 2102  df-cleq 2108  df-clel 2111  df-nfc 2245  df-v 2660  df-un 3043  df-br 3898  df-opab 3958  df-co 4516 This theorem is referenced by:  relcoi1  5038
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