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Mirrors > Home > MPE Home > Th. List > vtoclg | Structured version Visualization version GIF version |
Description: Implicit substitution of a class expression for a setvar variable. (Contributed by NM, 17-Apr-1995.) Avoid ax-12 2171. (Revised by SN, 20-Apr-2024.) |
Ref | Expression |
---|---|
vtoclg.1 | ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) |
vtoclg.2 | ⊢ 𝜑 |
Ref | Expression |
---|---|
vtoclg | ⊢ (𝐴 ∈ 𝑉 → 𝜓) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | elisset 2820 | . 2 ⊢ (𝐴 ∈ 𝑉 → ∃𝑥 𝑥 = 𝐴) | |
2 | vtoclg.2 | . . . 4 ⊢ 𝜑 | |
3 | vtoclg.1 | . . . 4 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) | |
4 | 2, 3 | mpbii 232 | . . 3 ⊢ (𝑥 = 𝐴 → 𝜓) |
5 | 4 | exlimiv 1933 | . 2 ⊢ (∃𝑥 𝑥 = 𝐴 → 𝜓) |
6 | 1, 5 | syl 17 | 1 ⊢ (𝐴 ∈ 𝑉 → 𝜓) |
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