Theorem con1bii2 33179

Description: A contraposition inference. (Contributed by ML, 18-Oct-2020.)

Hypothesis

Ref	Expression
con1bii2.1	|- ( -. ph <-> ps )

Assertion

Ref	Expression
con1bii2	|- ( ph <-> -. ps )

Proof of Theorem con1bii2

Step	Hyp	Ref	Expression
1		con1bii2.1	. . 3 |- ( -. ph <-> ps )
2	1	con1bii 346	. 2 |- ( -. ps <-> ph )
3	2	bicomi 214	1 |- ( ph <-> -. ps )

Syntax hints:   -. wn 3   <-> wb 196

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 197

This theorem is referenced by: (None)