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| Mirrors > Home > NFE Home > Th. List > imp | GIF version | ||
| Description: Importation inference. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Eric Schmidt, 22-Dec-2006.) |
| Ref | Expression |
|---|---|
| imp.1 | ⊢ (φ → (ψ → χ)) |
| Ref | Expression |
|---|---|
| imp | ⊢ ((φ ∧ ψ) → χ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-an 360 | . 2 ⊢ ((φ ∧ ψ) ↔ ¬ (φ → ¬ ψ)) | |
| 2 | imp.1 | . . 3 ⊢ (φ → (ψ → χ)) | |
| 3 | 2 | impi 140 | . 2 ⊢ (¬ (φ → ¬ ψ) → χ) |
| 4 | 1, 3 | sylbi 187 | 1 ⊢ ((φ ∧ ψ) → χ) |
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