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| Mirrors > Home > ILE Home > Th. List > elrab | GIF version | ||
| Description: Membership in a restricted class abstraction, using implicit substitution. (Contributed by NM, 21-May-1999.) | 
| Ref | Expression | 
|---|---|
| elrab.1 | ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) | 
| Ref | Expression | 
|---|---|
| elrab | ⊢ (𝐴 ∈ {𝑥 ∈ 𝐵 ∣ 𝜑} ↔ (𝐴 ∈ 𝐵 ∧ 𝜓)) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | nfcv 2339 | . 2 ⊢ Ⅎ𝑥𝐴 | |
| 2 | nfcv 2339 | . 2 ⊢ Ⅎ𝑥𝐵 | |
| 3 | nfv 1542 | . 2 ⊢ Ⅎ𝑥𝜓 | |
| 4 | elrab.1 | . 2 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓)) | |
| 5 | 1, 2, 3, 4 | elrabf 2918 | 1 ⊢ (𝐴 ∈ {𝑥 ∈ 𝐵 ∣ 𝜑} ↔ (𝐴 ∈ 𝐵 ∧ 𝜓)) | 
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