Theorem pm4.67 417

Description: Theorem *4.67 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)

Assertion

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

Proof of Theorem pm4.67

Step	Hyp	Ref	Expression
1		pm4.63 410	1 |- (-. (-. ph -> -. ps) <-> (-. ph /\ ps))

This proof depends on syntax axioms:  -. wn 3   -> wi 4   <-> wb 176   /\ wa 358

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 177  df-an 360

This theorem is used by: (None)