This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.

Metamath Proof Explorer

Theorem 7nn0

Description: 7 is a nonnegative integer. (Contributed by Mario Carneiro, 19-Apr-2015)

Ref Expression
Assertion 7nn0 
|- 7 e. NN0

Proof

Step Hyp Ref Expression
1 7nn 
 |-  7 e. NN
2 1 nnnn0i 
 |-  7 e. NN0