Theorem 0xnn0

Description: Zero is an extended nonnegative integer. (Contributed by AV, 10-Dec-2020)

	Ref	Expression
Assertion	0xnn0	⊢ 0 ∈ ℕ0*

Proof

Step	Hyp	Ref	Expression
1		nn0ssxnn0	⊢ ℕ0 ⊆ ℕ0*
2		0nn0	⊢ 0 ∈ ℕ0
3	1 2	sselii	⊢ 0 ∈ ℕ0*