Theorem eleq2w2 2758

Description: A weaker version of eleq2 2851 (but stronger than ax-9 2152 and elequ2 2157) that uses ax-12 2212 to avoid ax-8 2144 and df-clel 2837. Compare eleq2w 2846, whose setvars appear where the class variables are in this theorem, and vice versa. (Contributed by BJ, 24-Jun-2019.) Strengthen from setvar variables to class variables. (Revised by WL and SN, 23-Aug-2024.)

Assertion

Ref	Expression
eleq2w2	⊢ (𝐴 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵))

Distinct variable groups:   𝑥,𝐴   𝑥,𝐵

Proof of Theorem eleq2w2

Step	Hyp	Ref	Expression
1		dfcleq 2755	. . 3 ⊢ (𝐴 = 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵))
2	1	biimpi 218	. 2 ⊢ (𝐴 = 𝐵 → ∀𝑥(𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵))
3	2	19.21bi 2224	1 ⊢ (𝐴 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵))

Syntax hints:   → wi 4   ↔ wb 208  ∀wal 1558   = wceq 1560   ∈ wcel 2142

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1815  ax-4 1829  ax-5 1930  ax-6 1987  ax-7 2028  ax-9 2152  ax-12 2212  ax-ext 2734

This theorem depends on definitions:  df-bi 209  df-an 400  df-ex 1800  df-cleq 2754

This theorem is referenced by:  nfceqdf  2920  drnfc1  2943  drnfc2  2944  plngval  28981  r1omhfb  35405  fineqvrep  35407  fineqvpow  35408  fineqvac  35409  r1omhfbregs  35430  fvineqsneu  37902  sge0f1o  46953  f1omoOLD  49512  discthing  50079