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| Mirrors > Home > MPE Home > Th. List > dmeq | Structured version Visualization version GIF version | ||
| Description: Equality theorem for domain. (Contributed by NM, 11-Aug-1994.) |
| Ref | Expression |
|---|---|
| dmeq | ⊢ (𝐴 = 𝐵 → dom 𝐴 = dom 𝐵) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | dmss 5912 | . . 3 ⊢ (𝐴 ⊆ 𝐵 → dom 𝐴 ⊆ dom 𝐵) | |
| 2 | dmss 5912 | . . 3 ⊢ (𝐵 ⊆ 𝐴 → dom 𝐵 ⊆ dom 𝐴) | |
| 3 | 1, 2 | anim12i 613 | . 2 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴) → (dom 𝐴 ⊆ dom 𝐵 ∧ dom 𝐵 ⊆ dom 𝐴)) |
| 4 | eqss 3998 | . 2 ⊢ (𝐴 = 𝐵 ↔ (𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴)) | |
| 5 | eqss 3998 | . 2 ⊢ (dom 𝐴 = dom 𝐵 ↔ (dom 𝐴 ⊆ dom 𝐵 ∧ dom 𝐵 ⊆ dom 𝐴)) | |
| 6 | 3, 4, 5 | 3imtr4i 292 | 1 ⊢ (𝐴 = 𝐵 → dom 𝐴 = dom 𝐵) |
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