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Theorem orbidi 932
Description: Disjunction distributes over the biconditional. An axiom of system DS in Vladimir Lifschitz, "On calculational proofs" (1998), http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.25.3384. (Contributed by NM, 8-Jan-2005.) (Proof shortened by Wolf Lammen, 4-Feb-2013.)
Assertion
Ref Expression
orbidi

Proof of Theorem orbidi
StepHypRef Expression
1 pm5.74 244 . 2
2 df-or 370 . 2
3 df-or 370 . . 3
4 df-or 370 . . 3
53, 4bibi12i 315 . 2
61, 2, 53bitr4i 277 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  ->wi 4  <->wb 184  \/wo 368
This theorem is referenced by:  pm5.7  934
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 185  df-or 370
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