Description: An element of a power class is a subclass. Deduction form of elpwi . (Contributed by David Moews, 1-May-2017)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | elpwid.1 | ⊢ ( 𝜑 → 𝐴 ∈ 𝒫 𝐵 ) | |
| Assertion | elpwid | ⊢ ( 𝜑 → 𝐴 ⊆ 𝐵 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | elpwid.1 | ⊢ ( 𝜑 → 𝐴 ∈ 𝒫 𝐵 ) | |
| 2 | elpwi | ⊢ ( 𝐴 ∈ 𝒫 𝐵 → 𝐴 ⊆ 𝐵 ) | |
| 3 | 1 2 | syl | ⊢ ( 𝜑 → 𝐴 ⊆ 𝐵 ) |