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Related theorems GIF version |
| Description: Elimination of a conjunct. Theorem *3.26 (Simp) of [WhiteheadRussell] p. 112. |
| Ref | Expression |
|---|---|
| pm3.26 | ⊢ ((φ ⋀ ψ) → φ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-an 225 | . 2 ⊢ ((φ ⋀ ψ) ↔ ¬ (φ → ¬ ψ)) | |
| 2 | pm3.26im 139 | . 2 ⊢ (¬ (φ → ¬ ψ) → φ) | |
| 3 | 1, 2 | sylbi 199 | 1 ⊢ ((φ ⋀ ψ) → φ) |