Theorem 3orass 922

Description: Associative law for triple disjunction. (Contributed by NM, 8-Apr-1994.)

Assertion

Ref	Expression
3orass	|- ( ( ph \/ ps \/ ch ) <-> ( ph \/ ( ps \/ ch ) ) )

Proof of Theorem 3orass

Step	Hyp	Ref	Expression
1		df-3or 920	. 2 |- ( ( ph \/ ps \/ ch ) <-> ( ( ph \/ ps ) \/ ch ) )
2		orass 716	. 2 |- ( ( ( ph \/ ps ) \/ ch ) <-> ( ph \/ ( ps \/ ch ) ) )
3	1, 2	bitri 182	1 |- ( ( ph \/ ps \/ ch ) <-> ( ph \/ ( ps \/ ch ) ) )

Syntax hints:   <-> wb 103   \/ wo 661   \/ w3o 918

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 662

This theorem depends on definitions:  df-bi 115  df-3or 920

This theorem is referenced by:  3orrot  925  3orcomb  928  3mix1  1107  sotritric  4079  sotritrieq  4080  ordtriexmid  4265  acexmidlemcase  5527  nntri3or  6095  nntri2  6096  elnnz  8361  elznn0  8366  elznn  8367  zapne  8422  nn01to3  8702  elxr  8850  bezoutlemmain  10387