| Metamath Proof Explorer |
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Related theorems GIF version |
| Description: A useful inference for substituting definitions into an equality. |
| Ref | Expression |
|---|---|
| eqeq12d.1 | ⊢ (φ → A = B) |
| eqeq12d.2 | ⊢ (φ → C = D) |
| Ref | Expression |
|---|---|
| eqeq12d | ⊢ (φ → (A = C ↔ B = D)) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | eqeq12d.1 | . . 3 ⊢ (φ → A = B) | |
| 2 | 1 | eqeq1d 1526 | . 2 ⊢ (φ → (A = C ↔ B = C)) |
| 3 | eqeq12d.2 | . . 3 ⊢ (φ → C = D) | |
| 4 | 3 | eqeq2d 1529 | . 2 ⊢ (φ → (B = C ↔ B = D)) |
| 5 | 2, 4 | bitrd 531 | 1 ⊢ (φ → (A = C ↔ B = D)) |