Theorem fal 1338

Description: The truth value ⊥ is refutable. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Mel L. O'Cat, 11-Mar-2012.)

Assertion

Ref	Expression
fal	⊢ ¬ ⊥

Proof of Theorem fal

Step	Hyp	Ref	Expression
1		tru 1335	. . 3 ⊢ ⊤
2	1	notnoti 634	. 2 ⊢ ¬ ¬ ⊤
3		df-fal 1337	. 2 ⊢ (⊥ ↔ ¬ ⊤)
4	2, 3	mtbir 660	1 ⊢ ¬ ⊥

Syntax hints:  ¬ wn 3  ⊤wtru 1332  ⊥wfal 1336

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 603  ax-in2 604

This theorem depends on definitions:  df-bi 116  df-tru 1334  df-fal 1337

This theorem is referenced by:  nbfal  1342  bifal  1344  falim  1345  dfnot  1349  notfal  1392  alnex  1475  csbprc  3403  bdnth  13021