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Theorem uniin 4861
 Description: The class union of the intersection of two classes. Exercise 4.12(n) of [Mendelson] p. 235. See uniinqs 8376 for a condition where equality holds. (Contributed by NM, 4-Dec-2003.) (Proof shortened by Andrew Salmon, 29-Jun-2011.)
Assertion
Ref Expression
uniin (𝐴𝐵) ⊆ ( 𝐴 𝐵)

Proof of Theorem uniin
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 19.40 1883 . . . 4 (∃𝑦((𝑥𝑦𝑦𝐴) ∧ (𝑥𝑦𝑦𝐵)) → (∃𝑦(𝑥𝑦𝑦𝐴) ∧ ∃𝑦(𝑥𝑦𝑦𝐵)))
2 elin 4168 . . . . . . 7 (𝑦 ∈ (𝐴𝐵) ↔ (𝑦𝐴𝑦𝐵))
32anbi2i 624 . . . . . 6 ((𝑥𝑦𝑦 ∈ (𝐴𝐵)) ↔ (𝑥𝑦 ∧ (𝑦𝐴𝑦𝐵)))
4 anandi 674 . . . . . 6 ((𝑥𝑦 ∧ (𝑦𝐴𝑦𝐵)) ↔ ((𝑥𝑦𝑦𝐴) ∧ (𝑥𝑦𝑦𝐵)))
53, 4bitri 277 . . . . 5 ((𝑥𝑦𝑦 ∈ (𝐴𝐵)) ↔ ((𝑥𝑦𝑦𝐴) ∧ (𝑥𝑦𝑦𝐵)))
65exbii 1844 . . . 4 (∃𝑦(𝑥𝑦𝑦 ∈ (𝐴𝐵)) ↔ ∃𝑦((𝑥𝑦𝑦𝐴) ∧ (𝑥𝑦𝑦𝐵)))
7 eluni 4840 . . . . 5 (𝑥 𝐴 ↔ ∃𝑦(𝑥𝑦𝑦𝐴))
8 eluni 4840 . . . . 5 (𝑥 𝐵 ↔ ∃𝑦(𝑥𝑦𝑦𝐵))
97, 8anbi12i 628 . . . 4 ((𝑥 𝐴𝑥 𝐵) ↔ (∃𝑦(𝑥𝑦𝑦𝐴) ∧ ∃𝑦(𝑥𝑦𝑦𝐵)))
101, 6, 93imtr4i 294 . . 3 (∃𝑦(𝑥𝑦𝑦 ∈ (𝐴𝐵)) → (𝑥 𝐴𝑥 𝐵))
11 eluni 4840 . . 3 (𝑥 (𝐴𝐵) ↔ ∃𝑦(𝑥𝑦𝑦 ∈ (𝐴𝐵)))
12 elin 4168 . . 3 (𝑥 ∈ ( 𝐴 𝐵) ↔ (𝑥 𝐴𝑥 𝐵))
1310, 11, 123imtr4i 294 . 2 (𝑥 (𝐴𝐵) → 𝑥 ∈ ( 𝐴 𝐵))
1413ssriv 3970 1 (𝐴𝐵) ⊆ ( 𝐴 𝐵)
 Colors of variables: wff setvar class Syntax hints:   ∧ wa 398  ∃wex 1776   ∈ wcel 2110   ∩ cin 3934   ⊆ wss 3935  ∪ cuni 4837 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1907  ax-6 1966  ax-7 2011  ax-8 2112  ax-9 2120  ax-10 2141  ax-11 2157  ax-12 2173  ax-ext 2793 This theorem depends on definitions:  df-bi 209  df-an 399  df-or 844  df-tru 1536  df-ex 1777  df-nf 1781  df-sb 2066  df-clab 2800  df-cleq 2814  df-clel 2893  df-nfc 2963  df-v 3496  df-in 3942  df-ss 3951  df-uni 4838 This theorem is referenced by:  uniinqs  8376  psss  17823  tgval  21562  mapdunirnN  38785
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