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| Mirrors > Home > MPE Home > Th. List > eliun | Structured version Visualization version GIF version | ||
| Description: Membership in indexed union. (Contributed by NM, 3-Sep-2003.) |
| Ref | Expression |
|---|---|
| eliun | ⊢ (𝐴 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑥 ∈ 𝐵 𝐴 ∈ 𝐶) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | elex 3501 | . 2 ⊢ (𝐴 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 → 𝐴 ∈ V) | |
| 2 | elex 3501 | . . 3 ⊢ (𝐴 ∈ 𝐶 → 𝐴 ∈ V) | |
| 3 | 2 | rexlimivw 3151 | . 2 ⊢ (∃𝑥 ∈ 𝐵 𝐴 ∈ 𝐶 → 𝐴 ∈ V) |
| 4 | eleq1 2829 | . . . 4 ⊢ (𝑦 = 𝐴 → (𝑦 ∈ 𝐶 ↔ 𝐴 ∈ 𝐶)) | |
| 5 | 4 | rexbidv 3179 | . . 3 ⊢ (𝑦 = 𝐴 → (∃𝑥 ∈ 𝐵 𝑦 ∈ 𝐶 ↔ ∃𝑥 ∈ 𝐵 𝐴 ∈ 𝐶)) |
| 6 | df-iun 4993 | . . 3 ⊢ ∪ 𝑥 ∈ 𝐵 𝐶 = {𝑦 ∣ ∃𝑥 ∈ 𝐵 𝑦 ∈ 𝐶} | |
| 7 | 5, 6 | elab2g 3680 | . 2 ⊢ (𝐴 ∈ V → (𝐴 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑥 ∈ 𝐵 𝐴 ∈ 𝐶)) |
| 8 | 1, 3, 7 | pm5.21nii 378 | 1 ⊢ (𝐴 ∈ ∪ 𝑥 ∈ 𝐵 𝐶 ↔ ∃𝑥 ∈ 𝐵 𝐴 ∈ 𝐶) |
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