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Theorem nfsbxy 1861
 Description: Similar to hbsb 1866 but with an extra distinct variable constraint, on 𝑥 and 𝑦. (Contributed by Jim Kingdon, 19-Mar-2018.)
Hypothesis
Ref Expression
nfsbxy.1 𝑧𝜑
Assertion
Ref Expression
nfsbxy 𝑧[𝑦 / 𝑥]𝜑
Distinct variable groups:   𝑥,𝑦   𝑦,𝑧
Allowed substitution hints:   𝜑(𝑥,𝑦,𝑧)

Proof of Theorem nfsbxy
StepHypRef Expression
1 ax-bndl 1440 . 2 (∀𝑧 𝑧 = 𝑥 ∨ (∀𝑧 𝑧 = 𝑦 ∨ ∀𝑥𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦)))
2 nfs1v 1858 . . . 4 𝑧[𝑦 / 𝑧]𝜑
3 drsb1 1722 . . . . 5 (∀𝑧 𝑧 = 𝑥 → ([𝑦 / 𝑧]𝜑 ↔ [𝑦 / 𝑥]𝜑))
43drnf2 1664 . . . 4 (∀𝑧 𝑧 = 𝑥 → (Ⅎ𝑧[𝑦 / 𝑧]𝜑 ↔ Ⅎ𝑧[𝑦 / 𝑥]𝜑))
52, 4mpbii 146 . . 3 (∀𝑧 𝑧 = 𝑥 → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
6 a16nf 1789 . . . 4 (∀𝑧 𝑧 = 𝑦 → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
7 df-nf 1391 . . . . . 6 (Ⅎ𝑧 𝑥 = 𝑦 ↔ ∀𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦))
87albii 1400 . . . . 5 (∀𝑥𝑧 𝑥 = 𝑦 ↔ ∀𝑥𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦))
9 sb5 1810 . . . . . 6 ([𝑦 / 𝑥]𝜑 ↔ ∃𝑥(𝑥 = 𝑦𝜑))
10 nfa1 1475 . . . . . . 7 𝑥𝑥𝑧 𝑥 = 𝑦
11 sp 1442 . . . . . . . 8 (∀𝑥𝑧 𝑥 = 𝑦 → Ⅎ𝑧 𝑥 = 𝑦)
12 nfsbxy.1 . . . . . . . . 9 𝑧𝜑
1312a1i 9 . . . . . . . 8 (∀𝑥𝑧 𝑥 = 𝑦 → Ⅎ𝑧𝜑)
1411, 13nfand 1501 . . . . . . 7 (∀𝑥𝑧 𝑥 = 𝑦 → Ⅎ𝑧(𝑥 = 𝑦𝜑))
1510, 14nfexd 1686 . . . . . 6 (∀𝑥𝑧 𝑥 = 𝑦 → Ⅎ𝑧𝑥(𝑥 = 𝑦𝜑))
169, 15nfxfrd 1405 . . . . 5 (∀𝑥𝑧 𝑥 = 𝑦 → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
178, 16sylbir 133 . . . 4 (∀𝑥𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦) → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
186, 17jaoi 669 . . 3 ((∀𝑧 𝑧 = 𝑦 ∨ ∀𝑥𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦)) → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
195, 18jaoi 669 . 2 ((∀𝑧 𝑧 = 𝑥 ∨ (∀𝑧 𝑧 = 𝑦 ∨ ∀𝑥𝑧(𝑥 = 𝑦 → ∀𝑧 𝑥 = 𝑦))) → Ⅎ𝑧[𝑦 / 𝑥]𝜑)
201, 19ax-mp 7 1 𝑧[𝑦 / 𝑥]𝜑
 Colors of variables: wff set class Syntax hints:   → wi 4   ∧ wa 102   ∨ wo 662  ∀wal 1283  Ⅎwnf 1390  ∃wex 1422  [wsb 1687 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468 This theorem depends on definitions:  df-bi 115  df-nf 1391  df-sb 1688 This theorem is referenced by:  nfsb  1865  sbalyz  1918  opelopabsb  4044  bezoutlemmain  10578
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