Metamath Proof Explorer

Theorem 0xnn0

Description: Zero is an extended nonnegative integer. (Contributed by AV, 10-Dec-2020)

Ref Expression
Assertion 0xnn0 
|- 0 e. NN0*

Proof

Step Hyp Ref Expression
1 nn0ssxnn0 
 |-  NN0 C_ NN0*
2 0nn0 
 |-  0 e. NN0
3 1 2 sselii 
 |-  0 e. NN0*