Theorem 2m1e1OLD

Description: Obsolete version of 2m1e1 as of 10-Jun-2026. (Contributed by David A. Wheeler, 4-Jan-2017) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	2m1e1OLD	|- ( 2 - 1 ) = 1

Proof

Step	Hyp	Ref	Expression
1		2cn	|- 2 e. CC
2		ax-1cn	|- 1 e. CC
3		1p1e2	|- ( 1 + 1 ) = 2
4	1 2 2 3	subaddrii	|- ( 2 - 1 ) = 1