Theorem clelsb4 2143

Description: Substitution applied to an atomic wff (class version of elsb4 1853). (Contributed by Jim Kingdon, 22-Nov-2018.)

Assertion

Ref	Expression
clelsb4	⊢ ([𝑥 / 𝑦]𝐴 ∈ 𝑦 ↔ 𝐴 ∈ 𝑥)

Distinct variable group:   𝑦,𝐴

Allowed substitution hint:   𝐴(𝑥)

Proof of Theorem clelsb4

Dummy variable 𝑤 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfv 1421	. . 3 ⊢ Ⅎ𝑦 𝐴 ∈ 𝑤
2	1	sbco2 1839	. 2 ⊢ ([𝑥 / 𝑦][𝑦 / 𝑤]𝐴 ∈ 𝑤 ↔ [𝑥 / 𝑤]𝐴 ∈ 𝑤)
3		nfv 1421	. . . 4 ⊢ Ⅎ𝑤 𝐴 ∈ 𝑦
4		eleq2 2101	. . . 4 ⊢ (𝑤 = 𝑦 → (𝐴 ∈ 𝑤 ↔ 𝐴 ∈ 𝑦))
5	3, 4	sbie 1674	. . 3 ⊢ ([𝑦 / 𝑤]𝐴 ∈ 𝑤 ↔ 𝐴 ∈ 𝑦)
6	5	sbbii 1648	. 2 ⊢ ([𝑥 / 𝑦][𝑦 / 𝑤]𝐴 ∈ 𝑤 ↔ [𝑥 / 𝑦]𝐴 ∈ 𝑦)
7		nfv 1421	. . 3 ⊢ Ⅎ𝑤 𝐴 ∈ 𝑥
8		eleq2 2101	. . 3 ⊢ (𝑤 = 𝑥 → (𝐴 ∈ 𝑤 ↔ 𝐴 ∈ 𝑥))
9	7, 8	sbie 1674	. 2 ⊢ ([𝑥 / 𝑤]𝐴 ∈ 𝑤 ↔ 𝐴 ∈ 𝑥)
10	2, 6, 9	3bitr3i 199	1 ⊢ ([𝑥 / 𝑦]𝐴 ∈ 𝑦 ↔ 𝐴 ∈ 𝑥)

Syntax hints:   ↔ wb 98   ∈ wcel 1393  [wsb 1645

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 630  ax-5 1336  ax-7 1337  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-8 1395  ax-10 1396  ax-11 1397  ax-i12 1398  ax-bndl 1399  ax-4 1400  ax-17 1419  ax-i9 1423  ax-ial 1427  ax-i5r 1428  ax-ext 2022

This theorem depends on definitions:  df-bi 110  df-nf 1350  df-sb 1646  df-cleq 2033  df-clel 2036

This theorem is referenced by:  peano1  4317  peano2  4318