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Description: Every power class contains the empty set. (Contributed by NM, 25-Oct-2007)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | 0elpw | ⊢ ∅ ∈ 𝒫 𝐴 |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | 0ss | ⊢ ∅ ⊆ 𝐴 | |
| 2 | 0ex | ⊢ ∅ ∈ V | |
| 3 | 2 | elpw | ⊢ ( ∅ ∈ 𝒫 𝐴 ↔ ∅ ⊆ 𝐴 ) |
| 4 | 1 3 | mpbir | ⊢ ∅ ∈ 𝒫 𝐴 |