Theorem bicom1 122

Description: Commutative law for equivalence. (Contributed by Wolf Lammen, 10-Nov-2012.)

Assertion

Ref	Expression
bicom1	|- ( ( ph <-> ps ) -> ( ps <-> ph ) )

Proof of Theorem bicom1

Step	Hyp	Ref	Expression
1		bi2 121	. 2 |- ( ( ph <-> ps ) -> ( ps -> ph ) )
2		bi1 111	. 2 |- ( ( ph <-> ps ) -> ( ph -> ps ) )
3	1, 2	impbid 120	1 |- ( ( ph <-> ps ) -> ( ps <-> ph ) )

Syntax hints:   -> wi 4   <-> wb 98

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101

This theorem depends on definitions:  df-bi 110

This theorem is referenced by:  bicomi  123  bicom  128  pm5.21ndd  621  cbvexdh  1801  elabgf2  9919