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Theorem oridm 495
Description: Idempotent law for disjunction. Theorem *4.25 of [WhiteheadRussell] p. 117. (The proof was shortened by Andrew Salmon, 16-Apr-2011.) (The proof was shortened by Wolf Lammen, 10-Mar-2013.)
Assertion
Ref Expression
oridm

Proof of Theorem oridm
StepHypRef Expression
1 pm1.2 494 . 2
2 pm2.07 383 . 2
31, 2impbii 178 1
Colors of variables: wff set class
Syntax hints:   wb 174   wo 356
This theorem is referenced by:  pm4.25 496  orordi 511  orordir 512  unidm 2776  r19.12sn 3129  preqsn 3200  suceloni 3924  tz7.48lem 5490  msq0i 7630  prmdvdsexp 9944  pdivsq 15953  TTOid 16677  FFOid 16680  pm11.7 20029
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 175  df-or 358
Copyright terms: Public domain