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Theorem ralxfrALT 4396
 Description: Transfer universal quantification from a variable 𝑥 to another variable 𝑦 contained in expression 𝐴. This proof does not use ralxfrd 4391. (Contributed by NM, 10-Jun-2005.) (Revised by Mario Carneiro, 15-Aug-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
ralxfr.1 (𝑦𝐶𝐴𝐵)
ralxfr.2 (𝑥𝐵 → ∃𝑦𝐶 𝑥 = 𝐴)
ralxfr.3 (𝑥 = 𝐴 → (𝜑𝜓))
Assertion
Ref Expression
ralxfrALT (∀𝑥𝐵 𝜑 ↔ ∀𝑦𝐶 𝜓)
Distinct variable groups:   𝜓,𝑥   𝜑,𝑦   𝑥,𝐴   𝑥,𝑦,𝐵   𝑥,𝐶
Allowed substitution hints:   𝜑(𝑥)   𝜓(𝑦)   𝐴(𝑦)   𝐶(𝑦)

Proof of Theorem ralxfrALT
StepHypRef Expression
1 ralxfr.1 . . . . 5 (𝑦𝐶𝐴𝐵)
2 ralxfr.3 . . . . . 6 (𝑥 = 𝐴 → (𝜑𝜓))
32rspcv 2789 . . . . 5 (𝐴𝐵 → (∀𝑥𝐵 𝜑𝜓))
41, 3syl 14 . . . 4 (𝑦𝐶 → (∀𝑥𝐵 𝜑𝜓))
54com12 30 . . 3 (∀𝑥𝐵 𝜑 → (𝑦𝐶𝜓))
65ralrimiv 2507 . 2 (∀𝑥𝐵 𝜑 → ∀𝑦𝐶 𝜓)
7 ralxfr.2 . . . 4 (𝑥𝐵 → ∃𝑦𝐶 𝑥 = 𝐴)
8 nfra1 2469 . . . . 5 𝑦𝑦𝐶 𝜓
9 nfv 1509 . . . . 5 𝑦𝜑
10 rsp 2483 . . . . . 6 (∀𝑦𝐶 𝜓 → (𝑦𝐶𝜓))
112biimprcd 159 . . . . . 6 (𝜓 → (𝑥 = 𝐴𝜑))
1210, 11syl6 33 . . . . 5 (∀𝑦𝐶 𝜓 → (𝑦𝐶 → (𝑥 = 𝐴𝜑)))
138, 9, 12rexlimd 2549 . . . 4 (∀𝑦𝐶 𝜓 → (∃𝑦𝐶 𝑥 = 𝐴𝜑))
147, 13syl5 32 . . 3 (∀𝑦𝐶 𝜓 → (𝑥𝐵𝜑))
1514ralrimiv 2507 . 2 (∀𝑦𝐶 𝜓 → ∀𝑥𝐵 𝜑)
166, 15impbii 125 1 (∀𝑥𝐵 𝜑 ↔ ∀𝑦𝐶 𝜓)
 Colors of variables: wff set class Syntax hints:   → wi 4   ↔ wb 104   = wceq 1332   ∈ wcel 1481  ∀wral 2417  ∃wrex 2418 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 1424  ax-7 1425  ax-gen 1426  ax-ie1 1470  ax-ie2 1471  ax-8 1483  ax-10 1484  ax-11 1485  ax-i12 1486  ax-bndl 1487  ax-4 1488  ax-17 1507  ax-i9 1511  ax-ial 1515  ax-i5r 1516  ax-ext 2122 This theorem depends on definitions:  df-bi 116  df-tru 1335  df-nf 1438  df-sb 1737  df-clab 2127  df-cleq 2133  df-clel 2136  df-nfc 2271  df-ral 2422  df-rex 2423  df-v 2691 This theorem is referenced by: (None)
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