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Theorem disjeq0 4456
Description: Two disjoint sets are equal iff both are empty. (Contributed by AV, 19-Jun-2022.)
Assertion
Ref Expression
disjeq0 ((𝐴𝐵) = ∅ → (𝐴 = 𝐵 ↔ (𝐴 = ∅ ∧ 𝐵 = ∅)))

Proof of Theorem disjeq0
StepHypRef Expression
1 ineq1 4213 . . . . . 6 (𝐴 = 𝐵 → (𝐴𝐵) = (𝐵𝐵))
2 inidm 4227 . . . . . 6 (𝐵𝐵) = 𝐵
31, 2eqtrdi 2793 . . . . 5 (𝐴 = 𝐵 → (𝐴𝐵) = 𝐵)
43eqeq1d 2739 . . . 4 (𝐴 = 𝐵 → ((𝐴𝐵) = ∅ ↔ 𝐵 = ∅))
5 eqtr 2760 . . . . . 6 ((𝐴 = 𝐵𝐵 = ∅) → 𝐴 = ∅)
6 simpr 484 . . . . . 6 ((𝐴 = 𝐵𝐵 = ∅) → 𝐵 = ∅)
75, 6jca 511 . . . . 5 ((𝐴 = 𝐵𝐵 = ∅) → (𝐴 = ∅ ∧ 𝐵 = ∅))
87ex 412 . . . 4 (𝐴 = 𝐵 → (𝐵 = ∅ → (𝐴 = ∅ ∧ 𝐵 = ∅)))
94, 8sylbid 240 . . 3 (𝐴 = 𝐵 → ((𝐴𝐵) = ∅ → (𝐴 = ∅ ∧ 𝐵 = ∅)))
109com12 32 . 2 ((𝐴𝐵) = ∅ → (𝐴 = 𝐵 → (𝐴 = ∅ ∧ 𝐵 = ∅)))
11 eqtr3 2763 . 2 ((𝐴 = ∅ ∧ 𝐵 = ∅) → 𝐴 = 𝐵)
1210, 11impbid1 225 1 ((𝐴𝐵) = ∅ → (𝐴 = 𝐵 ↔ (𝐴 = ∅ ∧ 𝐵 = ∅)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 206  wa 395   = wceq 1540  cin 3950  c0 4333
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2007  ax-8 2110  ax-9 2118  ax-ext 2708
This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1543  df-ex 1780  df-sb 2065  df-clab 2715  df-cleq 2729  df-clel 2816  df-rab 3437  df-v 3482  df-in 3958
This theorem is referenced by:  epnsym  9649
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