Theorem biortn 934

Description: A wff is equivalent to its negated disjunction with falsehood. (Contributed by NM, 9-Jul-2012.)

Assertion

Ref	Expression
biortn	⊢ (𝜑 → (𝜓 ↔ (¬ 𝜑 ∨ 𝜓)))

Proof of Theorem biortn

Step	Hyp	Ref	Expression
1		notnot 144	. 2 ⊢ (𝜑 → ¬ ¬ 𝜑)
2		biorf 933	. 2 ⊢ (¬ ¬ 𝜑 → (𝜓 ↔ (¬ 𝜑 ∨ 𝜓)))
3	1, 2	syl 17	1 ⊢ (𝜑 → (𝜓 ↔ (¬ 𝜑 ∨ 𝜓)))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 208   ∨ wo 843

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 209  df-or 844

This theorem is referenced by:  oranabs  996  xrdifh  30505  ballotlemfc0  31752  ballotlemfcc  31753  topdifinfindis  34629  topdifinffinlem  34630  4atlem3a  36735  4atlem3b  36736  ntrneineine1lem  40441