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Related theorems GIF version |
| Description: Importation inference. |
| Ref | Expression |
|---|---|
| imp.1 | ⊢ (φ → (ψ → χ)) |
| Ref | Expression |
|---|---|
| imp | ⊢ ((φ ∧ ψ) → χ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-an 198 | . 2 ⊢ ((φ ∧ ψ) ↔ ¬ (φ → ¬ ψ)) | |
| 2 | imp.1 | . . 3 ⊢ (φ → (ψ → χ)) | |
| 3 | 2 | impi 124 | . 2 ⊢ (¬ (φ → ¬ ψ) → χ) |
| 4 | 1, 3 | sylbi 174 | 1 ⊢ ((φ ∧ ψ) → χ) |