Theorem bi2.03 144

Description: Contraposition. Bidirectional version of con2 82.

Assertion

Ref	Expression
bi2.03	|- ((ph -> -. ps) <-> (ps -> -. ph))

Proof of Theorem bi2.03

Step	Hyp	Ref	Expression
1		con2 82	. 2 |- ((ph -> -. ps) -> (ps -> -. ph))
2		con2 82	. 2 |- ((ps -> -. ph) -> (ph -> -. ps))
3	1, 2	impbi 139	1 |- ((ph -> -. ps) <-> (ps -> -. ph))

Syntax hints:  -. wn 1   -> wi 2   <-> wb 127

This theorem is referenced by:  bicon2 403  ssconb 1598  oneqmini 2272

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

This theorem depends on definitions:  df-bi 128

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