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Related theorems GIF version |
| Description: A mixed syllogism inference from a biconditional and an implication. Useful for substituting an antecedent with a definition. |
| Ref | Expression |
|---|---|
| sylbi.1 | ⊢ (φ ↔ ψ) |
| sylbi.2 | ⊢ (ψ → χ) |
| Ref | Expression |
|---|---|
| sylbi | ⊢ (φ → χ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sylbi.1 | . . 3 ⊢ (φ ↔ ψ) | |
| 2 | 1 | biimpi 149 | . 2 ⊢ (φ → ψ) |
| 3 | sylbi.2 | . 2 ⊢ (ψ → χ) | |
| 4 | 2, 3 | syl 10 | 1 ⊢ (φ → χ) |