Metamath Proof Explorer


Theorem nn0negz

Description: The negative of a nonnegative integer is an integer. (Contributed by NM, 9-May-2004)

Ref Expression
Assertion nn0negz N0N

Proof

Step Hyp Ref Expression
1 nn0z N0N
2 znegcl NN
3 1 2 syl N0N