Description: The standard nonnegative integers are a subset of the extended nonnegative integers. (Contributed by AV, 10-Dec-2020)
Ref | Expression | ||
---|---|---|---|
Assertion | nn0ssxnn0 | |- NN0 C_ NN0* |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssun1 | |- NN0 C_ ( NN0 u. { +oo } ) |
|
2 | df-xnn0 | |- NN0* = ( NN0 u. { +oo } ) |
|
3 | 1 2 | sseqtrri | |- NN0 C_ NN0* |