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Theorem elsb3 1868
 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]𝑦𝑧𝑥𝑧)
Distinct variable group:   𝑦,𝑧

Proof of Theorem elsb3
Dummy variable 𝑤 is distinct from all other variables.
StepHypRef Expression
1 ax-17 1435 . . . . 5 (𝑦𝑧 → ∀𝑤 𝑦𝑧)
2 elequ1 1616 . . . . 5 (𝑤 = 𝑦 → (𝑤𝑧𝑦𝑧))
31, 2sbieh 1689 . . . 4 ([𝑦 / 𝑤]𝑤𝑧𝑦𝑧)
43sbbii 1664 . . 3 ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑦]𝑦𝑧)
5 ax-17 1435 . . . 4 (𝑤𝑧 → ∀𝑦 𝑤𝑧)
65sbco2h 1854 . . 3 ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑤]𝑤𝑧)
74, 6bitr3i 179 . 2 ([𝑥 / 𝑦]𝑦𝑧 ↔ [𝑥 / 𝑤]𝑤𝑧)
8 equsb1 1684 . . . 4 [𝑥 / 𝑤]𝑤 = 𝑥
9 elequ1 1616 . . . . 5 (𝑤 = 𝑥 → (𝑤𝑧𝑥𝑧))
109sbimi 1663 . . . 4 ([𝑥 / 𝑤]𝑤 = 𝑥 → [𝑥 / 𝑤](𝑤𝑧𝑥𝑧))
118, 10ax-mp 7 . . 3 [𝑥 / 𝑤](𝑤𝑧𝑥𝑧)
12 sbbi 1849 . . 3 ([𝑥 / 𝑤](𝑤𝑧𝑥𝑧) ↔ ([𝑥 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑤]𝑥𝑧))
1311, 12mpbi 137 . 2 ([𝑥 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑤]𝑥𝑧)
14 ax-17 1435 . . 3 (𝑥𝑧 → ∀𝑤 𝑥𝑧)
1514sbh 1675 . 2 ([𝑥 / 𝑤]𝑥𝑧𝑥𝑧)
167, 13, 153bitri 199 1 ([𝑥 / 𝑦]𝑦𝑧𝑥𝑧)
 Colors of variables: wff set class Syntax hints:   ↔ wb 102  [wsb 1661 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-io 640  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-10 1412  ax-11 1413  ax-i12 1414  ax-bndl 1415  ax-4 1416  ax-13 1420  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444 This theorem depends on definitions:  df-bi 114  df-nf 1366  df-sb 1662 This theorem is referenced by:  cvjust  2051
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