| Intuitionistic Logic Explorer |
< Previous
Next >
Nearby theorems |
||
| Mirrors > Home > ILE Home > Th. List > bitri | GIF version | ||
| Description: An inference from transitive law for logical equivalence. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 13-Oct-2012.) |
| Ref | Expression |
|---|---|
| bitri.1 | ⊢ (𝜑 ↔ 𝜓) |
| bitri.2 | ⊢ (𝜓 ↔ 𝜒) |
| Ref | Expression |
|---|---|
| bitri | ⊢ (𝜑 ↔ 𝜒) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | bitri.1 | . . . 4 ⊢ (𝜑 ↔ 𝜓) | |
| 2 | 1 | biimpi 120 | . . 3 ⊢ (𝜑 → 𝜓) |
| 3 | bitri.2 | . . 3 ⊢ (𝜓 ↔ 𝜒) | |
| 4 | 2, 3 | sylib 122 | . 2 ⊢ (𝜑 → 𝜒) |
| 5 | 3 | biimpri 133 | . . 3 ⊢ (𝜒 → 𝜓) |
| 6 | 5, 1 | sylibr 134 | . 2 ⊢ (𝜒 → 𝜑) |
| 7 | 4, 6 | impbii 126 | 1 ⊢ (𝜑 ↔ 𝜒) |
| Copyright terms: Public domain | W3C validator |