Theorem bi2.03 165

Description: Contraposition. Bidirectional version of con2 90.

Assertion

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

Proof of Theorem bi2.03

Step	Hyp	Ref	Expression
1		con2 90	. 2 |- ((ph -> -. ps) -> (ps -> -. ph))
2		con2 90	. 2 |- ((ps -> -. ph) -> (ph -> -. ps))
3	1, 2	impbi 157	1 |- ((ph -> -. ps) <-> (ps -> -. ph))

Syntax hints:  -. wn 2   -> wi 3   <-> wb 146

This theorem is referenced by:  pm4.14 352  pm4.15 353  con2bi 525  nicodraw 952  ssconb 2170  oneqmini 3017  kmlem4 4768  islp2 7747

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

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