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Theorem dedlemb 955
 Description: Lemma for iffalse 3486. (Contributed by NM, 15-May-1999.) (Proof shortened by Andrew Salmon, 7-May-2011.)
Assertion
Ref Expression
dedlemb 𝜑 → (𝜒 ↔ ((𝜓𝜑) ∨ (𝜒 ∧ ¬ 𝜑))))

Proof of Theorem dedlemb
StepHypRef Expression
1 olc 701 . . 3 ((𝜒 ∧ ¬ 𝜑) → ((𝜓𝜑) ∨ (𝜒 ∧ ¬ 𝜑)))
21expcom 115 . 2 𝜑 → (𝜒 → ((𝜓𝜑) ∨ (𝜒 ∧ ¬ 𝜑))))
3 pm2.21 607 . . . 4 𝜑 → (𝜑𝜒))
43adantld 276 . . 3 𝜑 → ((𝜓𝜑) → 𝜒))
5 simpl 108 . . . 4 ((𝜒 ∧ ¬ 𝜑) → 𝜒)
65a1i 9 . . 3 𝜑 → ((𝜒 ∧ ¬ 𝜑) → 𝜒))
74, 6jaod 707 . 2 𝜑 → (((𝜓𝜑) ∨ (𝜒 ∧ ¬ 𝜑)) → 𝜒))
82, 7impbid 128 1 𝜑 → (𝜒 ↔ ((𝜓𝜑) ∨ (𝜒 ∧ ¬ 𝜑))))
 Colors of variables: wff set class Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 103   ↔ wb 104   ∨ wo 698 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-in2 605  ax-io 699 This theorem depends on definitions:  df-bi 116 This theorem is referenced by:  iffalse  3486
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