Description: Every power class contains the empty set. (Contributed by NM, 25-Oct-2007)
Ref | Expression | ||
---|---|---|---|
Assertion | 0elpw | |- (/) e. ~P A |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0ss | |- (/) C_ A |
|
2 | 0ex | |- (/) e. _V |
|
3 | 2 | elpw | |- ( (/) e. ~P A <-> (/) C_ A ) |
4 | 1 3 | mpbir | |- (/) e. ~P A |