Theorem nnnn0

Description: A positive integer is a nonnegative integer. (Contributed by NM, 9-May-2004)

	Ref	Expression
Assertion	nnnn0	$$⊢A\in \mathbb{N}\to A\in {\mathbb{N}}_0$$

Proof

Step	Hyp	Ref	Expression
1		nnssnn0	$$⊢\mathbb{N}\subseteq {\mathbb{N}}_0$$
2	1	sseli	$$⊢A\in \mathbb{N}\to A\in {\mathbb{N}}_0$$