Theorem nnnn0d

Description: A positive integer is a nonnegative integer. (Contributed by Mario Carneiro, 27-May-2016)

	Ref	Expression
Hypothesis	nnnn0d.1	|- ( ph -> A e. NN )
Assertion	nnnn0d	|- ( ph -> A e. NN0 )

Proof

Step	Hyp	Ref	Expression
1		nnnn0d.1	|- ( ph -> A e. NN )
2		nnssnn0	|- NN C_ NN0
3	2 1	sseldi	|- ( ph -> A e. NN0 )