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Theorem biort 738
Description: A wff is disjoined with truth is true. (Contributed by NM, 23-May-1999.)
Assertion
Ref Expression
biort (𝜑 → (𝜑 ↔ (𝜑𝜓)))

Proof of Theorem biort
StepHypRef Expression
1 orc 633 . 2 (𝜑 → (𝜑𝜓))
2 ax-1 5 . 2 (𝜑 → ((𝜑𝜓) → 𝜑))
31, 2impbid2 131 1 (𝜑 → (𝜑 ↔ (𝜑𝜓)))
Colors of variables: wff set class
Syntax hints:  wi 4  wb 98  wo 629
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 630
This theorem depends on definitions:  df-bi 110
This theorem is referenced by:  pm5.55dc  819
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