Proof of Theorem opexg
| Step | Hyp | Ref
| Expression |
| 1 | | dfopg 3820 |
. 2
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → 〈𝐴, 𝐵〉 = {{𝐴}, {𝐴, 𝐵}}) |
| 2 | | elex 2785 |
. . . . 5
⊢ (𝐴 ∈ 𝑉 → 𝐴 ∈ V) |
| 3 | | snexg 4233 |
. . . . 5
⊢ (𝐴 ∈ V → {𝐴} ∈ V) |
| 4 | 2, 3 | syl 14 |
. . . 4
⊢ (𝐴 ∈ 𝑉 → {𝐴} ∈ V) |
| 5 | 4 | adantr 276 |
. . 3
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → {𝐴} ∈ V) |
| 6 | | elex 2785 |
. . . 4
⊢ (𝐵 ∈ 𝑊 → 𝐵 ∈ V) |
| 7 | | prexg 4260 |
. . . 4
⊢ ((𝐴 ∈ V ∧ 𝐵 ∈ V) → {𝐴, 𝐵} ∈ V) |
| 8 | 2, 6, 7 | syl2an 289 |
. . 3
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → {𝐴, 𝐵} ∈ V) |
| 9 | | prexg 4260 |
. . 3
⊢ (({𝐴} ∈ V ∧ {𝐴, 𝐵} ∈ V) → {{𝐴}, {𝐴, 𝐵}} ∈ V) |
| 10 | 5, 8, 9 | syl2anc 411 |
. 2
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → {{𝐴}, {𝐴, 𝐵}} ∈ V) |
| 11 | 1, 10 | eqeltrd 2283 |
1
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → 〈𝐴, 𝐵〉 ∈ V) |