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Theorem cleqh 2872
 Description: Establish equality between classes, using bound-variable hypotheses instead of distinct variable conditions. See also cleqf 2938. (Contributed by NM, 26-May-1993.) (Proof shortened by Wolf Lammen, 14-Nov-2019.) Remove dependency on ax-13 2407. (Revised by BJ, 30-Nov-2020.)
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 2764 . 2 (𝐴 = 𝐵 ↔ ∀𝑦(𝑦𝐴𝑦𝐵))
2 nfv 1994 . . 3 𝑦(𝑥𝐴𝑥𝐵)
3 cleqh.1 . . . . 5 (𝑦𝐴 → ∀𝑥 𝑦𝐴)
43nf5i 2178 . . . 4 𝑥 𝑦𝐴
5 cleqh.2 . . . . 5 (𝑦𝐵 → ∀𝑥 𝑦𝐵)
65nf5i 2178 . . . 4 𝑥 𝑦𝐵
74, 6nfbi 1984 . . 3 𝑥(𝑦𝐴𝑦𝐵)
8 eleq1w 2832 . . . 4 (𝑥 = 𝑦 → (𝑥𝐴𝑦𝐴))
9 eleq1w 2832 . . . 4 (𝑥 = 𝑦 → (𝑥𝐵𝑦𝐵))
108, 9bibi12d 334 . . 3 (𝑥 = 𝑦 → ((𝑥𝐴𝑥𝐵) ↔ (𝑦𝐴𝑦𝐵)))
112, 7, 10cbvalv1 2335 . 2 (∀𝑥(𝑥𝐴𝑥𝐵) ↔ ∀𝑦(𝑦𝐴𝑦𝐵))
121, 11bitr4i 267 1 (𝐴 = 𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 196  ∀wal 1628   = wceq 1630   ∈ wcel 2144 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1869  ax-4 1884  ax-5 1990  ax-6 2056  ax-7 2092  ax-9 2153  ax-10 2173  ax-11 2189  ax-12 2202  ax-ext 2750 This theorem depends on definitions:  df-bi 197  df-an 383  df-or 827  df-tru 1633  df-ex 1852  df-nf 1857  df-cleq 2763  df-clel 2766 This theorem is referenced by:  abeq2  2880  abbi  2885  cleqf  2938  abeq2f  2940  bj-abeq2  33103
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