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Theorem elimif 4566
Description: Elimination of a conditional operator contained in a wff 𝜓. (Contributed by NM, 15-Feb-2005.) (Proof shortened by NM, 25-Apr-2019.)
Hypotheses
Ref Expression
elimif.1 (if(𝜑, 𝐴, 𝐵) = 𝐴 → (𝜓𝜒))
elimif.2 (if(𝜑, 𝐴, 𝐵) = 𝐵 → (𝜓𝜃))
Assertion
Ref Expression
elimif (𝜓 ↔ ((𝜑𝜒) ∨ (¬ 𝜑𝜃)))

Proof of Theorem elimif
StepHypRef Expression
1 iftrue 4535 . . 3 (𝜑 → if(𝜑, 𝐴, 𝐵) = 𝐴)
2 elimif.1 . . 3 (if(𝜑, 𝐴, 𝐵) = 𝐴 → (𝜓𝜒))
31, 2syl 17 . 2 (𝜑 → (𝜓𝜒))
4 iffalse 4538 . . 3 𝜑 → if(𝜑, 𝐴, 𝐵) = 𝐵)
5 elimif.2 . . 3 (if(𝜑, 𝐴, 𝐵) = 𝐵 → (𝜓𝜃))
64, 5syl 17 . 2 𝜑 → (𝜓𝜃))
73, 6cases 1041 1 (𝜓 ↔ ((𝜑𝜒) ∨ (¬ 𝜑𝜃)))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 205  wa 395  wo 846   = wceq 1534  ifcif 4529
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1790  ax-4 1804  ax-5 1906  ax-6 1964  ax-7 2004  ax-8 2101  ax-9 2109  ax-ext 2699
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 847  df-ex 1775  df-sb 2061  df-clab 2706  df-cleq 2720  df-clel 2806  df-if 4530
This theorem is referenced by:  eqif  4570  elif  4572  ifel  4573  ftc1anclem5  37170  clsk1indlem2  43472
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