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Theorem difin0ss 3925
Description: Difference, intersection, and subclass relationship. (Contributed by NM, 30-Apr-1994.) (Proof shortened by Wolf Lammen, 30-Sep-2014.)
Assertion
Ref Expression
difin0ss (((𝐴𝐵) ∩ 𝐶) = ∅ → (𝐶𝐴𝐶𝐵))

Proof of Theorem difin0ss
Dummy variable 𝑥 is distinct from all other variables.
StepHypRef Expression
1 eq0 3910 . 2 (((𝐴𝐵) ∩ 𝐶) = ∅ ↔ ∀𝑥 ¬ 𝑥 ∈ ((𝐴𝐵) ∩ 𝐶))
2 iman 440 . . . . . 6 ((𝑥𝐶 → (𝑥𝐴𝑥𝐵)) ↔ ¬ (𝑥𝐶 ∧ ¬ (𝑥𝐴𝑥𝐵)))
3 elin 3779 . . . . . . 7 (𝑥 ∈ ((𝐴𝐵) ∩ 𝐶) ↔ (𝑥 ∈ (𝐴𝐵) ∧ 𝑥𝐶))
4 eldif 3570 . . . . . . . 8 (𝑥 ∈ (𝐴𝐵) ↔ (𝑥𝐴 ∧ ¬ 𝑥𝐵))
54anbi2ci 731 . . . . . . 7 ((𝑥 ∈ (𝐴𝐵) ∧ 𝑥𝐶) ↔ (𝑥𝐶 ∧ (𝑥𝐴 ∧ ¬ 𝑥𝐵)))
6 annim 441 . . . . . . . 8 ((𝑥𝐴 ∧ ¬ 𝑥𝐵) ↔ ¬ (𝑥𝐴𝑥𝐵))
76anbi2i 729 . . . . . . 7 ((𝑥𝐶 ∧ (𝑥𝐴 ∧ ¬ 𝑥𝐵)) ↔ (𝑥𝐶 ∧ ¬ (𝑥𝐴𝑥𝐵)))
83, 5, 73bitri 286 . . . . . 6 (𝑥 ∈ ((𝐴𝐵) ∩ 𝐶) ↔ (𝑥𝐶 ∧ ¬ (𝑥𝐴𝑥𝐵)))
92, 8xchbinxr 325 . . . . 5 ((𝑥𝐶 → (𝑥𝐴𝑥𝐵)) ↔ ¬ 𝑥 ∈ ((𝐴𝐵) ∩ 𝐶))
10 ax-2 7 . . . . 5 ((𝑥𝐶 → (𝑥𝐴𝑥𝐵)) → ((𝑥𝐶𝑥𝐴) → (𝑥𝐶𝑥𝐵)))
119, 10sylbir 225 . . . 4 𝑥 ∈ ((𝐴𝐵) ∩ 𝐶) → ((𝑥𝐶𝑥𝐴) → (𝑥𝐶𝑥𝐵)))
1211al2imi 1740 . . 3 (∀𝑥 ¬ 𝑥 ∈ ((𝐴𝐵) ∩ 𝐶) → (∀𝑥(𝑥𝐶𝑥𝐴) → ∀𝑥(𝑥𝐶𝑥𝐵)))
13 dfss2 3577 . . 3 (𝐶𝐴 ↔ ∀𝑥(𝑥𝐶𝑥𝐴))
14 dfss2 3577 . . 3 (𝐶𝐵 ↔ ∀𝑥(𝑥𝐶𝑥𝐵))
1512, 13, 143imtr4g 285 . 2 (∀𝑥 ¬ 𝑥 ∈ ((𝐴𝐵) ∩ 𝐶) → (𝐶𝐴𝐶𝐵))
161, 15sylbi 207 1 (((𝐴𝐵) ∩ 𝐶) = ∅ → (𝐶𝐴𝐶𝐵))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 384  wal 1478   = wceq 1480  wcel 1992  cdif 3557  cin 3559  wss 3560  c0 3896
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1841  ax-6 1890  ax-7 1937  ax-9 2001  ax-10 2021  ax-11 2036  ax-12 2049  ax-13 2250  ax-ext 2606
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1883  df-clab 2613  df-cleq 2619  df-clel 2622  df-nfc 2756  df-v 3193  df-dif 3563  df-in 3567  df-ss 3574  df-nul 3897
This theorem is referenced by:  tz7.7  5711  tfi  7001  lebnumlem3  22665
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