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Theorem disjif2 30920
Description: Property of a disjoint collection: if 𝐵(𝑥) and 𝐵(𝑌) = 𝐷 have a common element 𝑍, then 𝑥 = 𝑌. (Contributed by Thierry Arnoux, 6-Apr-2017.)
Hypotheses
Ref Expression
disjif2.1 𝑥𝐴
disjif2.2 𝑥𝐶
disjif2.3 (𝑥 = 𝑌𝐵 = 𝐶)
Assertion
Ref Expression
disjif2 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴) ∧ (𝑍𝐵𝑍𝐶)) → 𝑥 = 𝑌)
Distinct variable group:   𝑥,𝑌
Allowed substitution hints:   𝐴(𝑥)   𝐵(𝑥)   𝐶(𝑥)   𝑍(𝑥)

Proof of Theorem disjif2
Dummy variables 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 inelcm 4398 . 2 ((𝑍𝐵𝑍𝐶) → (𝐵𝐶) ≠ ∅)
2 disjif2.1 . . . . . . . 8 𝑥𝐴
32disjorsf 30919 . . . . . . 7 (Disj 𝑥𝐴 𝐵 ↔ ∀𝑦𝐴𝑧𝐴 (𝑦 = 𝑧 ∨ (𝑦 / 𝑥𝐵𝑧 / 𝑥𝐵) = ∅))
4 equequ1 2028 . . . . . . . . 9 (𝑦 = 𝑥 → (𝑦 = 𝑧𝑥 = 𝑧))
5 csbeq1 3835 . . . . . . . . . . . 12 (𝑦 = 𝑥𝑦 / 𝑥𝐵 = 𝑥 / 𝑥𝐵)
6 csbid 3845 . . . . . . . . . . . 12 𝑥 / 𝑥𝐵 = 𝐵
75, 6eqtrdi 2794 . . . . . . . . . . 11 (𝑦 = 𝑥𝑦 / 𝑥𝐵 = 𝐵)
87ineq1d 4145 . . . . . . . . . 10 (𝑦 = 𝑥 → (𝑦 / 𝑥𝐵𝑧 / 𝑥𝐵) = (𝐵𝑧 / 𝑥𝐵))
98eqeq1d 2740 . . . . . . . . 9 (𝑦 = 𝑥 → ((𝑦 / 𝑥𝐵𝑧 / 𝑥𝐵) = ∅ ↔ (𝐵𝑧 / 𝑥𝐵) = ∅))
104, 9orbi12d 916 . . . . . . . 8 (𝑦 = 𝑥 → ((𝑦 = 𝑧 ∨ (𝑦 / 𝑥𝐵𝑧 / 𝑥𝐵) = ∅) ↔ (𝑥 = 𝑧 ∨ (𝐵𝑧 / 𝑥𝐵) = ∅)))
11 eqeq2 2750 . . . . . . . . 9 (𝑧 = 𝑌 → (𝑥 = 𝑧𝑥 = 𝑌))
12 nfcv 2907 . . . . . . . . . . . 12 𝑥𝑌
13 disjif2.2 . . . . . . . . . . . 12 𝑥𝐶
14 disjif2.3 . . . . . . . . . . . 12 (𝑥 = 𝑌𝐵 = 𝐶)
1512, 13, 14csbhypf 3861 . . . . . . . . . . 11 (𝑧 = 𝑌𝑧 / 𝑥𝐵 = 𝐶)
1615ineq2d 4146 . . . . . . . . . 10 (𝑧 = 𝑌 → (𝐵𝑧 / 𝑥𝐵) = (𝐵𝐶))
1716eqeq1d 2740 . . . . . . . . 9 (𝑧 = 𝑌 → ((𝐵𝑧 / 𝑥𝐵) = ∅ ↔ (𝐵𝐶) = ∅))
1811, 17orbi12d 916 . . . . . . . 8 (𝑧 = 𝑌 → ((𝑥 = 𝑧 ∨ (𝐵𝑧 / 𝑥𝐵) = ∅) ↔ (𝑥 = 𝑌 ∨ (𝐵𝐶) = ∅)))
1910, 18rspc2v 3570 . . . . . . 7 ((𝑥𝐴𝑌𝐴) → (∀𝑦𝐴𝑧𝐴 (𝑦 = 𝑧 ∨ (𝑦 / 𝑥𝐵𝑧 / 𝑥𝐵) = ∅) → (𝑥 = 𝑌 ∨ (𝐵𝐶) = ∅)))
203, 19syl5bi 241 . . . . . 6 ((𝑥𝐴𝑌𝐴) → (Disj 𝑥𝐴 𝐵 → (𝑥 = 𝑌 ∨ (𝐵𝐶) = ∅)))
2120impcom 408 . . . . 5 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴)) → (𝑥 = 𝑌 ∨ (𝐵𝐶) = ∅))
2221ord 861 . . . 4 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴)) → (¬ 𝑥 = 𝑌 → (𝐵𝐶) = ∅))
2322necon1ad 2960 . . 3 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴)) → ((𝐵𝐶) ≠ ∅ → 𝑥 = 𝑌))
24233impia 1116 . 2 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴) ∧ (𝐵𝐶) ≠ ∅) → 𝑥 = 𝑌)
251, 24syl3an3 1164 1 ((Disj 𝑥𝐴 𝐵 ∧ (𝑥𝐴𝑌𝐴) ∧ (𝑍𝐵𝑍𝐶)) → 𝑥 = 𝑌)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wa 396  wo 844  w3a 1086   = wceq 1539  wcel 2106  wnfc 2887  wne 2943  wral 3064  csb 3832  cin 3886  c0 4256  Disj wdisj 5039
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1913  ax-6 1971  ax-7 2011  ax-8 2108  ax-9 2116  ax-10 2137  ax-11 2154  ax-12 2171  ax-ext 2709
This theorem depends on definitions:  df-bi 206  df-an 397  df-or 845  df-3an 1088  df-tru 1542  df-fal 1552  df-ex 1783  df-nf 1787  df-sb 2068  df-mo 2540  df-clab 2716  df-cleq 2730  df-clel 2816  df-nfc 2889  df-ne 2944  df-ral 3069  df-rmo 3071  df-rab 3073  df-v 3434  df-sbc 3717  df-csb 3833  df-dif 3890  df-in 3894  df-nul 4257  df-disj 5040
This theorem is referenced by:  disjabrexf  30922
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