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| Mirrors > Home > PE Home > Th. List > ndtruee-P3.18 | |||
| Description: Natural Deduction: '⊤' Elimination Rule.
Rules 17 and 18 allow us to write '(⊤ → 𝜑)' as a synonym for stating "'𝜑' is true" (or, more precisely, deducable). |
| Ref | Expression |
|---|---|
| ndtruee-P3.18.1 | ⊢ (⊤ → 𝜑) |
| Ref | Expression |
|---|---|
| ndtruee-P3.18 | ⊢ 𝜑 |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | true-P2.14 156 | . 2 ⊢ ⊤ | |
| 2 | ndtruee-P3.18.1 | . 2 ⊢ (⊤ → 𝜑) | |
| 3 | 1, 2 | ax-MP 14 | 1 ⊢ 𝜑 |
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