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Theorem csbco3g 3977
 Description: Composition of two class substitutions. (Contributed by NM, 27-Nov-2005.) (Revised by Mario Carneiro, 11-Nov-2016.)
Hypothesis
Ref Expression
sbcco3g.1 (𝑥 = 𝐴𝐵 = 𝐶)
Assertion
Ref Expression
csbco3g (𝐴𝑉𝐴 / 𝑥𝐵 / 𝑦𝐷 = 𝐶 / 𝑦𝐷)
Distinct variable groups:   𝑥,𝐴   𝑥,𝐶   𝑥,𝐷
Allowed substitution hints:   𝐴(𝑦)   𝐵(𝑥,𝑦)   𝐶(𝑦)   𝐷(𝑦)   𝑉(𝑥,𝑦)

Proof of Theorem csbco3g
StepHypRef Expression
1 csbnestg 3975 . 2 (𝐴𝑉𝐴 / 𝑥𝐵 / 𝑦𝐷 = 𝐴 / 𝑥𝐵 / 𝑦𝐷)
2 elex 3203 . . . 4 (𝐴𝑉𝐴 ∈ V)
3 nfcvd 2768 . . . . 5 (𝐴 ∈ V → 𝑥𝐶)
4 sbcco3g.1 . . . . 5 (𝑥 = 𝐴𝐵 = 𝐶)
53, 4csbiegf 3543 . . . 4 (𝐴 ∈ V → 𝐴 / 𝑥𝐵 = 𝐶)
62, 5syl 17 . . 3 (𝐴𝑉𝐴 / 𝑥𝐵 = 𝐶)
76csbeq1d 3526 . 2 (𝐴𝑉𝐴 / 𝑥𝐵 / 𝑦𝐷 = 𝐶 / 𝑦𝐷)
81, 7eqtrd 2660 1 (𝐴𝑉𝐴 / 𝑥𝐵 / 𝑦𝐷 = 𝐶 / 𝑦𝐷)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   = wceq 1480   ∈ wcel 1992  Vcvv 3191  ⦋csb 3519 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1841  ax-6 1890  ax-7 1937  ax-9 2001  ax-10 2021  ax-11 2036  ax-12 2049  ax-13 2250  ax-ext 2606 This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1038  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1883  df-clab 2613  df-cleq 2619  df-clel 2622  df-nfc 2756  df-v 3193  df-sbc 3423  df-csb 3520 This theorem is referenced by: (None)
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