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Theorem subtr2 36297
Description: Transitivity of implicit substitution into a wff. (Contributed by Jeff Hankins, 19-Sep-2009.) (Proof shortened by Mario Carneiro, 11-Dec-2016.)
Hypotheses
Ref Expression
subtr.1 𝑥𝐴
subtr.2 𝑥𝐵
subtr2.3 𝑥𝜓
subtr2.4 𝑥𝜒
subtr2.5 (𝑥 = 𝐴 → (𝜑𝜓))
subtr2.6 (𝑥 = 𝐵 → (𝜑𝜒))
Assertion
Ref Expression
subtr2 ((𝐴𝐶𝐵𝐷) → (𝐴 = 𝐵 → (𝜓𝜒)))

Proof of Theorem subtr2
StepHypRef Expression
1 subtr.1 . . 3 𝑥𝐴
2 subtr.2 . . . . 5 𝑥𝐵
31, 2nfeq 2916 . . . 4 𝑥 𝐴 = 𝐵
4 subtr2.3 . . . . 5 𝑥𝜓
5 subtr2.4 . . . . 5 𝑥𝜒
64, 5nfbi 1900 . . . 4 𝑥(𝜓𝜒)
73, 6nfim 1893 . . 3 𝑥(𝐴 = 𝐵 → (𝜓𝜒))
8 eqeq1 2738 . . . 4 (𝑥 = 𝐴 → (𝑥 = 𝐵𝐴 = 𝐵))
9 subtr2.5 . . . . 5 (𝑥 = 𝐴 → (𝜑𝜓))
109bibi1d 343 . . . 4 (𝑥 = 𝐴 → ((𝜑𝜒) ↔ (𝜓𝜒)))
118, 10imbi12d 344 . . 3 (𝑥 = 𝐴 → ((𝑥 = 𝐵 → (𝜑𝜒)) ↔ (𝐴 = 𝐵 → (𝜓𝜒))))
12 subtr2.6 . . 3 (𝑥 = 𝐵 → (𝜑𝜒))
131, 7, 11, 12vtoclgf 3568 . 2 (𝐴𝐶 → (𝐴 = 𝐵 → (𝜓𝜒)))
1413adantr 480 1 ((𝐴𝐶𝐵𝐷) → (𝐴 = 𝐵 → (𝜓𝜒)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 206  wa 395   = wceq 1536  wnf 1779  wcel 2105  wnfc 2887
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1791  ax-4 1805  ax-5 1907  ax-6 1964  ax-7 2004  ax-8 2107  ax-9 2115  ax-10 2138  ax-11 2154  ax-12 2174  ax-ext 2705
This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-tru 1539  df-ex 1776  df-nf 1780  df-sb 2062  df-clab 2712  df-cleq 2726  df-clel 2813  df-nfc 2889  df-v 3479
This theorem is referenced by: (None)
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