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Theorem efald 1334
Description: Deduction based on reductio ad absurdum. (Contributed by Mario Carneiro, 9-Feb-2017.)
Hypothesis
Ref Expression
efald.1 ((φ ¬ ψ) → ⊥ )
Assertion
Ref Expression
efald (φψ)

Proof of Theorem efald
StepHypRef Expression
1 efald.1 . . 3 ((φ ¬ ψ) → ⊥ )
21inegd 1333 . 2 (φ → ¬ ¬ ψ)
32notnotrd 105 1 (φψ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4   wa 358  wfal 1317
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 177  df-an 360  df-tru 1319  df-fal 1320
This theorem is referenced by: (None)
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