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Theorem cbvralf 2674
Description: Rule used to change bound variables, using implicit substitution. (Contributed by NM, 7-Mar-2004.) (Revised by Mario Carneiro, 9-Oct-2016.)
Hypotheses
Ref Expression
cbvralf.1 𝑥𝐴
cbvralf.2 𝑦𝐴
cbvralf.3 𝑦𝜑
cbvralf.4 𝑥𝜓
cbvralf.5 (𝑥 = 𝑦 → (𝜑𝜓))
Assertion
Ref Expression
cbvralf (∀𝑥𝐴 𝜑 ↔ ∀𝑦𝐴 𝜓)

Proof of Theorem cbvralf
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 nfv 1508 . . . 4 𝑧(𝑥𝐴𝜑)
2 cbvralf.1 . . . . . 6 𝑥𝐴
32nfcri 2293 . . . . 5 𝑥 𝑧𝐴
4 nfs1v 1919 . . . . 5 𝑥[𝑧 / 𝑥]𝜑
53, 4nfim 1552 . . . 4 𝑥(𝑧𝐴 → [𝑧 / 𝑥]𝜑)
6 eleq1 2220 . . . . 5 (𝑥 = 𝑧 → (𝑥𝐴𝑧𝐴))
7 sbequ12 1751 . . . . 5 (𝑥 = 𝑧 → (𝜑 ↔ [𝑧 / 𝑥]𝜑))
86, 7imbi12d 233 . . . 4 (𝑥 = 𝑧 → ((𝑥𝐴𝜑) ↔ (𝑧𝐴 → [𝑧 / 𝑥]𝜑)))
91, 5, 8cbval 1734 . . 3 (∀𝑥(𝑥𝐴𝜑) ↔ ∀𝑧(𝑧𝐴 → [𝑧 / 𝑥]𝜑))
10 cbvralf.2 . . . . . 6 𝑦𝐴
1110nfcri 2293 . . . . 5 𝑦 𝑧𝐴
12 cbvralf.3 . . . . . 6 𝑦𝜑
1312nfsb 1926 . . . . 5 𝑦[𝑧 / 𝑥]𝜑
1411, 13nfim 1552 . . . 4 𝑦(𝑧𝐴 → [𝑧 / 𝑥]𝜑)
15 nfv 1508 . . . 4 𝑧(𝑦𝐴𝜓)
16 eleq1 2220 . . . . 5 (𝑧 = 𝑦 → (𝑧𝐴𝑦𝐴))
17 sbequ 1820 . . . . . 6 (𝑧 = 𝑦 → ([𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑))
18 cbvralf.4 . . . . . . 7 𝑥𝜓
19 cbvralf.5 . . . . . . 7 (𝑥 = 𝑦 → (𝜑𝜓))
2018, 19sbie 1771 . . . . . 6 ([𝑦 / 𝑥]𝜑𝜓)
2117, 20bitrdi 195 . . . . 5 (𝑧 = 𝑦 → ([𝑧 / 𝑥]𝜑𝜓))
2216, 21imbi12d 233 . . . 4 (𝑧 = 𝑦 → ((𝑧𝐴 → [𝑧 / 𝑥]𝜑) ↔ (𝑦𝐴𝜓)))
2314, 15, 22cbval 1734 . . 3 (∀𝑧(𝑧𝐴 → [𝑧 / 𝑥]𝜑) ↔ ∀𝑦(𝑦𝐴𝜓))
249, 23bitri 183 . 2 (∀𝑥(𝑥𝐴𝜑) ↔ ∀𝑦(𝑦𝐴𝜓))
25 df-ral 2440 . 2 (∀𝑥𝐴 𝜑 ↔ ∀𝑥(𝑥𝐴𝜑))
26 df-ral 2440 . 2 (∀𝑦𝐴 𝜓 ↔ ∀𝑦(𝑦𝐴𝜓))
2724, 25, 263bitr4i 211 1 (∀𝑥𝐴 𝜑 ↔ ∀𝑦𝐴 𝜓)
Colors of variables: wff set class
Syntax hints:  wi 4  wb 104  wal 1333  wnf 1440  [wsb 1742  wcel 2128  wnfc 2286  wral 2435
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 699  ax-5 1427  ax-7 1428  ax-gen 1429  ax-ie1 1473  ax-ie2 1474  ax-8 1484  ax-10 1485  ax-11 1486  ax-i12 1487  ax-bndl 1489  ax-4 1490  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2139
This theorem depends on definitions:  df-bi 116  df-nf 1441  df-sb 1743  df-cleq 2150  df-clel 2153  df-nfc 2288  df-ral 2440
This theorem is referenced by:  cbvral  2676  ffnfvf  5628
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