Theorem trubifal 1307

Description: A ↔ identity. (Contributed by David A. Wheeler, 23-Feb-2018.)

Assertion

Ref	Expression
trubifal	⊢ ((⊤ ↔ ⊥) ↔ ⊥)

Proof of Theorem trubifal

Step	Hyp	Ref	Expression
1		dfbi2 368	. 2 ⊢ ((⊤ ↔ ⊥) ↔ ((⊤ → ⊥) ∧ (⊥ → ⊤)))
2		truimfal 1301	. . 3 ⊢ ((⊤ → ⊥) ↔ ⊥)
3		falimtru 1302	. . 3 ⊢ ((⊥ → ⊤) ↔ ⊤)
4	2, 3	anbi12i 433	. 2 ⊢ (((⊤ → ⊥) ∧ (⊥ → ⊤)) ↔ (⊥ ∧ ⊤))
5		falantru 1294	. 2 ⊢ ((⊥ ∧ ⊤) ↔ ⊥)
6	1, 4, 5	3bitri 195	1 ⊢ ((⊤ ↔ ⊥) ↔ ⊥)

Syntax hints:   → wi 4   ∧ wa 97   ↔ wb 98  ⊤wtru 1244  ⊥wfal 1248

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-in1 544  ax-in2 545

This theorem depends on definitions:  df-bi 110  df-tru 1246  df-fal 1249

This theorem is referenced by:  falbitru  1308