Theorem elsb3 1901

Description: Substitution applied to an atomic membership wff. (Contributed by NM, 7-Nov-2006.) (Proof shortened by Andrew Salmon, 14-Jun-2011.)

Assertion

Ref	Expression
elsb3	⊢ ([𝑥 / 𝑦]𝑦 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧)

Distinct variable group:   𝑦,𝑧

Proof of Theorem elsb3

Dummy variable 𝑤 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax-17 1465	. . . . 5 ⊢ (𝑦 ∈ 𝑧 → ∀𝑤 𝑦 ∈ 𝑧)
2		elequ1 1648	. . . . 5 ⊢ (𝑤 = 𝑦 → (𝑤 ∈ 𝑧 ↔ 𝑦 ∈ 𝑧))
3	1, 2	sbieh 1721	. . . 4 ⊢ ([𝑦 / 𝑤]𝑤 ∈ 𝑧 ↔ 𝑦 ∈ 𝑧)
4	3	sbbii 1696	. . 3 ⊢ ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤 ∈ 𝑧 ↔ [𝑥 / 𝑦]𝑦 ∈ 𝑧)
5		ax-17 1465	. . . 4 ⊢ (𝑤 ∈ 𝑧 → ∀𝑦 𝑤 ∈ 𝑧)
6	5	sbco2h 1887	. . 3 ⊢ ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤 ∈ 𝑧 ↔ [𝑥 / 𝑤]𝑤 ∈ 𝑧)
7	4, 6	bitr3i 185	. 2 ⊢ ([𝑥 / 𝑦]𝑦 ∈ 𝑧 ↔ [𝑥 / 𝑤]𝑤 ∈ 𝑧)
8		equsb1 1716	. . . 4 ⊢ [𝑥 / 𝑤]𝑤 = 𝑥
9		elequ1 1648	. . . . 5 ⊢ (𝑤 = 𝑥 → (𝑤 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧))
10	9	sbimi 1695	. . . 4 ⊢ ([𝑥 / 𝑤]𝑤 = 𝑥 → [𝑥 / 𝑤](𝑤 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧))
11	8, 10	ax-mp 7	. . 3 ⊢ [𝑥 / 𝑤](𝑤 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧)
12		sbbi 1882	. . 3 ⊢ ([𝑥 / 𝑤](𝑤 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧) ↔ ([𝑥 / 𝑤]𝑤 ∈ 𝑧 ↔ [𝑥 / 𝑤]𝑥 ∈ 𝑧))
13	11, 12	mpbi 144	. 2 ⊢ ([𝑥 / 𝑤]𝑤 ∈ 𝑧 ↔ [𝑥 / 𝑤]𝑥 ∈ 𝑧)
14		ax-17 1465	. . 3 ⊢ (𝑥 ∈ 𝑧 → ∀𝑤 𝑥 ∈ 𝑧)
15	14	sbh 1707	. 2 ⊢ ([𝑥 / 𝑤]𝑥 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧)
16	7, 13, 15	3bitri 205	1 ⊢ ([𝑥 / 𝑦]𝑦 ∈ 𝑧 ↔ 𝑥 ∈ 𝑧)

Syntax hints:   ↔ wb 104  [wsb 1693

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 666  ax-5 1382  ax-7 1383  ax-gen 1384  ax-ie1 1428  ax-ie2 1429  ax-8 1441  ax-10 1442  ax-11 1443  ax-i12 1444  ax-bndl 1445  ax-4 1446  ax-13 1450  ax-17 1465  ax-i9 1469  ax-ial 1473  ax-i5r 1474

This theorem depends on definitions:  df-bi 116  df-nf 1396  df-sb 1694

This theorem is referenced by:  cvjust  2084