| Metamath Proof Explorer |
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Related theorems GIF version |
| Description: A mixed syllogism inference from an implication and a biconditional. Useful for substituting a consequent with a definition. |
| Ref | Expression |
|---|---|
| sylibr.1 | ⊢ (φ → ψ) |
| sylibr.2 | ⊢ (χ ↔ ψ) |
| Ref | Expression |
|---|---|
| sylibr | ⊢ (φ → χ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sylibr.1 | . 2 ⊢ (φ → ψ) | |
| 2 | sylibr.2 | . . 3 ⊢ (χ ↔ ψ) | |
| 3 | 2 | biimpr 134 | . 2 ⊢ (ψ → χ) |
| 4 | 1, 3 | syl 12 | 1 ⊢ (φ → χ) |