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Related theorems GIF version |
| Description: Equality implies equivalence of membership. |
| Ref | Expression |
|---|---|
| eleq1 | ⊢ (A = B → (A ∈ C ↔ B ∈ C)) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | cleq2 1110 | . . . 4 ⊢ (A = B → (x = A ↔ x = B)) | |
| 2 | 1 | anbi1d 469 | . . 3 ⊢ (A = B → ((x = A ∧ x ∈ C) ↔ (x = B ∧ x ∈ C))) |
| 3 | 2 | biexdv 936 | . 2 ⊢ (A = B → (∃x(x = A ∧ x ∈ C) ↔ ∃x(x = B ∧ x ∈ C))) |
| 4 | df-clel 1099 | . 2 ⊢ (A ∈ C ↔ ∃x(x = A ∧ x ∈ C)) | |
| 5 | df-clel 1099 | . 2 ⊢ (B ∈ C ↔ ∃x(x = B ∧ x ∈ C)) | |
| 6 | 3, 4, 5 | 3bitr4g 428 | 1 ⊢ (A = B → (A ∈ C ↔ B ∈ C)) |