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Theorem ax467to4 2170
Description: Re-derivation of ax-4 2135 from ax467 2169. Only propositional calculus is used by the re-derivation. (Contributed by NM, 19-Nov-2006.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
ax467to4 (xφφ)

Proof of Theorem ax467to4
StepHypRef Expression
1 ax-1 6 . 2 (xφ → (xx ¬ xxφxφ))
2 ax467 2169 . 2 ((xx ¬ xxφxφ) → φ)
31, 2syl 15 1 (xφφ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wal 1540
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-7 1734  ax-4 2135  ax-5o 2136  ax-6o 2137
This theorem is referenced by: (None)
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