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Theorem pm2.74 819
Description: Theorem *2.74 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Andrew Salmon, 7-May-2011.)
Assertion
Ref Expression
pm2.74 ((ψφ) → (((φ ψ) χ) → (φ χ)))

Proof of Theorem pm2.74
StepHypRef Expression
1 orel2 372 . . 3 ψ → ((φ ψ) → φ))
2 ax-1 6 . . 3 (φ → ((φ ψ) → φ))
31, 2ja 153 . 2 ((ψφ) → ((φ ψ) → φ))
43orim1d 812 1 ((ψφ) → (((φ ψ) χ) → (φ χ)))
Colors of variables: wff setvar class
Syntax hints:  wi 4   wo 357
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-or 359  df-an 360
This theorem is referenced by: (None)
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