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Theorem ornld 1088
 Description: Selecting one statement from a disjunction if one of the disjuncted statements is false. (Contributed by AV, 6-Sep-2018.) (Proof shortened by AV, 13-Oct-2018.) (Proof shortened by Wolf Lammen, 19-Jan-2020.)
Assertion
Ref Expression
ornld (𝜑 → (((𝜑 → (𝜃𝜏)) ∧ ¬ 𝜃) → 𝜏))

Proof of Theorem ornld
StepHypRef Expression
1 pm3.35 837 . . 3 ((𝜑 ∧ (𝜑 → (𝜃𝜏))) → (𝜃𝜏))
21ord 895 . 2 ((𝜑 ∧ (𝜑 → (𝜃𝜏))) → (¬ 𝜃𝜏))
32expimpd 447 1 (𝜑 → (((𝜑 → (𝜃𝜏)) ∧ ¬ 𝜃) → 𝜏))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 386   ∨ wo 878 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8 This theorem depends on definitions:  df-bi 199  df-an 387  df-or 879 This theorem is referenced by:  friendshipgt3  27809  ralralimp  42175
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