Theorem nn0sscn

Description: Nonnegative integers are a subset of the complex numbers. (Contributed by NM, 9-May-2004) Reduce dependencies on axioms. (Revised by Steven Nguyen, 8-Oct-2022)

	Ref	Expression
Assertion	nn0sscn	|- NN0 C_ CC

Proof

Step	Hyp	Ref	Expression
1		df-n0	|- NN0 = ( NN u. { 0 } )
2		nnsscn	|- NN C_ CC
3		0cn	|- 0 e. CC
4		snssi	|- ( 0 e. CC -> { 0 } C_ CC )
5	3 4	ax-mp	|- { 0 } C_ CC
6	2 5	unssi	|- ( NN u. { 0 } ) C_ CC
7	1 6	eqsstri	|- NN0 C_ CC