Metamath Proof Explorer

Theorem nnzd

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

Ref Expression
Hypothesis nnzd.1 
|- ( ph -> A e. NN )
Assertion nnzd 
|- ( ph -> A e. ZZ )

Proof

Step Hyp Ref Expression
1 nnzd.1 
 |-  ( ph -> A e. NN )
2 1 nnnn0d 
 |-  ( ph -> A e. NN0 )
3 2 nn0zd 
 |-  ( ph -> A e. ZZ )