Theorem pm3.1 755

Description: Theorem *3.1 of [WhiteheadRussell] p. 111. The converse holds for decidable propositions, as seen at anordc 958. (Contributed by NM, 3-Jan-2005.) (Revised by Mario Carneiro, 31-Jan-2015.)

Assertion

Ref	Expression
pm3.1	|- ( ( ph /\ ps ) -> -. ( -. ph \/ -. ps ) )

Proof of Theorem pm3.1

Step	Hyp	Ref	Expression
1		pm3.14 754	. 2 |- ( ( -. ph \/ -. ps ) -> -. ( ph /\ ps ) )
2	1	con2i 628	1 |- ( ( ph /\ ps ) -> -. ( -. ph \/ -. ps ) )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 104   \/ wo 709

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-io 710

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  inssun  3404