Theorem trunortruOLD

Description: Obsolete version of trunortru as of 7-Dec-2023. (Contributed by Remi, 25-Oct-2023) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	trunortruOLD	⊢ ( ( ⊤ ⊽ ⊤ ) ↔ ⊥ )

Proof

Step	Hyp	Ref	Expression
1		df-nor	⊢ ( ( ⊤ ⊽ ⊤ ) ↔ ¬ ( ⊤ ∨ ⊤ ) )
2		tru	⊢ ⊤
3	2	orci	⊢ ( ⊤ ∨ ⊤ )
4	3	notnoti	⊢ ¬ ¬ ( ⊤ ∨ ⊤ )
5	4	bifal	⊢ ( ¬ ( ⊤ ∨ ⊤ ) ↔ ⊥ )
6	1 5	bitri	⊢ ( ( ⊤ ⊽ ⊤ ) ↔ ⊥ )