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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 5808 | . . 3 ⊢ (𝐴 ⊆ 𝐵 → dom 𝐴 ⊆ dom 𝐵) | |
2 | dmss 5808 | . . 3 ⊢ (𝐵 ⊆ 𝐴 → dom 𝐵 ⊆ dom 𝐴) | |
3 | 1, 2 | anim12i 612 | . 2 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴) → (dom 𝐴 ⊆ dom 𝐵 ∧ dom 𝐵 ⊆ dom 𝐴)) |
4 | eqss 3940 | . 2 ⊢ (𝐴 = 𝐵 ↔ (𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴)) | |
5 | eqss 3940 | . 2 ⊢ (dom 𝐴 = dom 𝐵 ↔ (dom 𝐴 ⊆ dom 𝐵 ∧ dom 𝐵 ⊆ dom 𝐴)) | |
6 | 3, 4, 5 | 3imtr4i 291 | 1 ⊢ (𝐴 = 𝐵 → dom 𝐴 = dom 𝐵) |
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