Theorem nnzd

Description: A nonnegative integer is an integer. (Contributed by Mario Carneiro, 28-May-2016)

	Ref	Expression
Hypothesis	nnzd.1	⊢ ( 𝜑 → 𝐴 ∈ ℕ )
Assertion	nnzd	⊢ ( 𝜑 → 𝐴 ∈ ℤ )

Proof

Step	Hyp	Ref	Expression
1		nnzd.1	⊢ ( 𝜑 → 𝐴 ∈ ℕ )
2	1	nnnn0d	⊢ ( 𝜑 → 𝐴 ∈ ℕ0 )
3	2	nn0zd	⊢ ( 𝜑 → 𝐴 ∈ ℤ )