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Theorem ecased 1224
Description: Deduction form of disjunctive syllogism. (Contributed by Jim Kingdon, 9-Dec-2017.)
Hypotheses
Ref Expression
ecased.1 (φ → ¬ χ)
ecased.2 (φ → (ψ χ))
Assertion
Ref Expression
ecased (φψ)

Proof of Theorem ecased
StepHypRef Expression
1 ecased.1 . . 3 (φ → ¬ χ)
2 ecased.2 . . 3 (φ → (ψ χ))
31, 2jca 290 . 2 (φ → (¬ χ (ψ χ)))
4 orel2 632 . . 3 χ → ((ψ χ) → ψ))
54imp 115 . 2 ((¬ χ (ψ χ)) → ψ)
63, 5syl 14 1 (φψ)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4   wa 97   wo 616
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in2 533  ax-io 617
This theorem depends on definitions:  df-bi 110
This theorem is referenced by:  ecase23d  1225  preleq  4215  ordsuc  4223  sotri3  4648
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