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Theorem sbco2v 1876
Description: This is a version of sbco2 1894 where 𝑧 is distinct from 𝑥. (Contributed by Jim Kingdon, 12-Feb-2018.)
Hypothesis
Ref Expression
sbco2v.1 (𝜑 → ∀𝑧𝜑)
Assertion
Ref Expression
sbco2v ([𝑦 / 𝑧][𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑)
Distinct variable group:   𝑥,𝑧
Allowed substitution hints:   𝜑(𝑥,𝑦,𝑧)

Proof of Theorem sbco2v
Dummy variable 𝑤 is distinct from all other variables.
StepHypRef Expression
1 sbco2v.1 . . . 4 (𝜑 → ∀𝑧𝜑)
21sbco2vlem 1875 . . 3 ([𝑤 / 𝑧][𝑧 / 𝑥]𝜑 ↔ [𝑤 / 𝑥]𝜑)
32sbbii 1702 . 2 ([𝑦 / 𝑤][𝑤 / 𝑧][𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑤][𝑤 / 𝑥]𝜑)
4 ax-17 1471 . . 3 ([𝑧 / 𝑥]𝜑 → ∀𝑤[𝑧 / 𝑥]𝜑)
54sbco2vlem 1875 . 2 ([𝑦 / 𝑤][𝑤 / 𝑧][𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑧][𝑧 / 𝑥]𝜑)
6 ax-17 1471 . . 3 (𝜑 → ∀𝑤𝜑)
76sbco2vlem 1875 . 2 ([𝑦 / 𝑤][𝑤 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑)
83, 5, 73bitr3i 209 1 ([𝑦 / 𝑧][𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑)
Colors of variables: wff set class
Syntax hints:  wi 4  wb 104  wal 1294  [wsb 1699
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 668  ax-5 1388  ax-7 1389  ax-gen 1390  ax-ie1 1434  ax-ie2 1435  ax-8 1447  ax-10 1448  ax-11 1449  ax-i12 1450  ax-4 1452  ax-17 1471  ax-i9 1475  ax-ial 1479  ax-i5r 1480
This theorem depends on definitions:  df-bi 116  df-nf 1402  df-sb 1700
This theorem is referenced by:  nfsb  1877  equsb3  1880  sbn  1881  sbim  1882  sbor  1883  sban  1884  sbco2vd  1896  sbco3v  1898  sbcom2v2  1917  sbcom2  1918  dfsb7  1922  sb7f  1923  sbal  1931  sbal1  1933  sbex  1935
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