Theorem ontrciOLD

Description: Obsolete version of ontr as of 28-Dec-2024. (Contributed by NM, 11-Jun-1994) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	on.1	|- A e. On
Assertion	ontrciOLD	|- Tr A

Proof

Step	Hyp	Ref	Expression
1		on.1	|- A e. On
2		ontr	|- ( A e. On -> Tr A )
3	1 2	ax-mp	|- Tr A