Theorem neg1z

Description: -1 is an integer. (Contributed by David A. Wheeler, 5-Dec-2018)

	Ref	Expression
Assertion	neg1z	$$⊢-1\in \mathbb{Z}$$

Proof

Step	Hyp	Ref	Expression
1		1nn	$$⊢1\in \mathbb{N}$$
2		nnnegz	$$⊢1\in \mathbb{N}\to -1\in \mathbb{Z}$$
3	1 2	ax-mp	$$⊢-1\in \mathbb{Z}$$