Theorem pm4.67 241

Description: Theorem *4.67 of [WhiteheadRussell] p. 120.

Assertion

Ref	Expression
pm4.67	|- (-. (-. ph -> -. ps) <-> (-. ph /\ ps))

Proof of Theorem pm4.67

Step	Hyp	Ref	Expression
1		pm4.63 228	1 |- (-. (-. ph -> -. ps) <-> (-. ph /\ ps))

Syntax hints:  -. wn 2   -> wi 3   <-> wb 146   /\ wa 223

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-an 225

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