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Theorem cleqh 2217
Description: Establish equality between classes, using bound-variable hypotheses instead of distinct variable conditions. See also cleqf 2282. (Contributed by NM, 5-Aug-1993.)
Hypotheses
Ref Expression
cleqh.1 (𝑦𝐴 → ∀𝑥 𝑦𝐴)
cleqh.2 (𝑦𝐵 → ∀𝑥 𝑦𝐵)
Assertion
Ref Expression
cleqh (𝐴 = 𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
Distinct variable groups:   𝑦,𝐴   𝑦,𝐵   𝑥,𝑦
Allowed substitution hints:   𝐴(𝑥)   𝐵(𝑥)

Proof of Theorem cleqh
StepHypRef Expression
1 dfcleq 2111 . 2 (𝐴 = 𝐵 ↔ ∀𝑦(𝑦𝐴𝑦𝐵))
2 ax-17 1491 . . . 4 ((𝑥𝐴𝑥𝐵) → ∀𝑦(𝑥𝐴𝑥𝐵))
3 dfbi2 385 . . . . 5 ((𝑦𝐴𝑦𝐵) ↔ ((𝑦𝐴𝑦𝐵) ∧ (𝑦𝐵𝑦𝐴)))
4 cleqh.1 . . . . . . 7 (𝑦𝐴 → ∀𝑥 𝑦𝐴)
5 cleqh.2 . . . . . . 7 (𝑦𝐵 → ∀𝑥 𝑦𝐵)
64, 5hbim 1509 . . . . . 6 ((𝑦𝐴𝑦𝐵) → ∀𝑥(𝑦𝐴𝑦𝐵))
75, 4hbim 1509 . . . . . 6 ((𝑦𝐵𝑦𝐴) → ∀𝑥(𝑦𝐵𝑦𝐴))
86, 7hban 1511 . . . . 5 (((𝑦𝐴𝑦𝐵) ∧ (𝑦𝐵𝑦𝐴)) → ∀𝑥((𝑦𝐴𝑦𝐵) ∧ (𝑦𝐵𝑦𝐴)))
93, 8hbxfrbi 1433 . . . 4 ((𝑦𝐴𝑦𝐵) → ∀𝑥(𝑦𝐴𝑦𝐵))
10 eleq1 2180 . . . . . 6 (𝑥 = 𝑦 → (𝑥𝐴𝑦𝐴))
11 eleq1 2180 . . . . . 6 (𝑥 = 𝑦 → (𝑥𝐵𝑦𝐵))
1210, 11bibi12d 234 . . . . 5 (𝑥 = 𝑦 → ((𝑥𝐴𝑥𝐵) ↔ (𝑦𝐴𝑦𝐵)))
1312biimpd 143 . . . 4 (𝑥 = 𝑦 → ((𝑥𝐴𝑥𝐵) → (𝑦𝐴𝑦𝐵)))
142, 9, 13cbv3h 1706 . . 3 (∀𝑥(𝑥𝐴𝑥𝐵) → ∀𝑦(𝑦𝐴𝑦𝐵))
1512equcoms 1669 . . . . 5 (𝑦 = 𝑥 → ((𝑥𝐴𝑥𝐵) ↔ (𝑦𝐴𝑦𝐵)))
1615biimprd 157 . . . 4 (𝑦 = 𝑥 → ((𝑦𝐴𝑦𝐵) → (𝑥𝐴𝑥𝐵)))
179, 2, 16cbv3h 1706 . . 3 (∀𝑦(𝑦𝐴𝑦𝐵) → ∀𝑥(𝑥𝐴𝑥𝐵))
1814, 17impbii 125 . 2 (∀𝑥(𝑥𝐴𝑥𝐵) ↔ ∀𝑦(𝑦𝐴𝑦𝐵))
191, 18bitr4i 186 1 (𝐴 = 𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
Colors of variables: wff set class
Syntax hints:  wi 4  wa 103  wb 104  wal 1314   = wceq 1316  wcel 1465
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-5 1408  ax-7 1409  ax-gen 1410  ax-ie1 1454  ax-ie2 1455  ax-8 1467  ax-4 1472  ax-17 1491  ax-i9 1495  ax-ial 1499  ax-i5r 1500  ax-ext 2099
This theorem depends on definitions:  df-bi 116  df-nf 1422  df-cleq 2110  df-clel 2113
This theorem is referenced by:  abeq2  2226
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