Theorem pm4.25 244

Description: Theorem *4.25 of [WhiteheadRussell] p. 117.

Assertion

Ref	Expression
pm4.25	|- (ph <-> (ph \/ ph))

Proof of Theorem pm4.25

Step	Hyp	Ref	Expression
1		oridm 243	. 2 |- ((ph \/ ph) <-> ph)
2	1	bicomi 172	1 |- (ph <-> (ph \/ ph))

Syntax hints:   <-> wb 146   \/ wo 222

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7

This theorem depends on definitions:  df-bi 147  df-or 224

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