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Theorem csbeq2d 3817
 Description: Formula-building deduction for class substitution. (Contributed by NM, 22-Nov-2005.) (Revised by Mario Carneiro, 1-Sep-2015.)
Hypotheses
Ref Expression
csbeq2d.1 𝑥𝜑
csbeq2d.2 (𝜑𝐵 = 𝐶)
Assertion
Ref Expression
csbeq2d (𝜑𝐴 / 𝑥𝐵 = 𝐴 / 𝑥𝐶)

Proof of Theorem csbeq2d
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 csbeq2d.1 . . . 4 𝑥𝜑
2 csbeq2d.2 . . . . 5 (𝜑𝐵 = 𝐶)
32eleq2d 2868 . . . 4 (𝜑 → (𝑦𝐵𝑦𝐶))
41, 3sbcbid 3755 . . 3 (𝜑 → ([𝐴 / 𝑥]𝑦𝐵[𝐴 / 𝑥]𝑦𝐶))
54abbidv 2860 . 2 (𝜑 → {𝑦[𝐴 / 𝑥]𝑦𝐵} = {𝑦[𝐴 / 𝑥]𝑦𝐶})
6 df-csb 3812 . 2 𝐴 / 𝑥𝐵 = {𝑦[𝐴 / 𝑥]𝑦𝐵}
7 df-csb 3812 . 2 𝐴 / 𝑥𝐶 = {𝑦[𝐴 / 𝑥]𝑦𝐶}
85, 6, 73eqtr4g 2856 1 (𝜑𝐴 / 𝑥𝐵 = 𝐴 / 𝑥𝐶)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   = wceq 1522  Ⅎwnf 1765   ∈ wcel 2081  {cab 2775  [wsbc 3706  ⦋csb 3811 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1777  ax-4 1791  ax-5 1888  ax-6 1947  ax-7 1992  ax-8 2083  ax-9 2091  ax-12 2141  ax-ext 2769 This theorem depends on definitions:  df-bi 208  df-an 397  df-ex 1762  df-nf 1766  df-sb 2043  df-clab 2776  df-cleq 2788  df-clel 2863  df-sbc 3707  df-csb 3812 This theorem is referenced by:  csbeq2dv  3818  poimirlem26  34449
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