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Metamath Proof Explorer

Theorem pm5.13

Description: Theorem *5.13 of WhiteheadRussell p. 123. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 14-Nov-2012)

Ref Expression
Assertion pm5.13 
|- ( ( ph -> ps ) \/ ( ps -> ph ) )

Proof

Step Hyp Ref Expression
1 pm5.14 
 |-  ( ( ph -> ps ) \/ ( ps -> ph ) )