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Theorem nfpr 3450
Description: Bound-variable hypothesis builder for unordered pairs. (Contributed by NM, 14-Nov-1995.)
Hypotheses
Ref Expression
nfpr.1 𝑥𝐴
nfpr.2 𝑥𝐵
Assertion
Ref Expression
nfpr 𝑥{𝐴, 𝐵}

Proof of Theorem nfpr
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 dfpr2 3425 . 2 {𝐴, 𝐵} = {𝑦 ∣ (𝑦 = 𝐴𝑦 = 𝐵)}
2 nfpr.1 . . . . 5 𝑥𝐴
32nfeq2 2231 . . . 4 𝑥 𝑦 = 𝐴
4 nfpr.2 . . . . 5 𝑥𝐵
54nfeq2 2231 . . . 4 𝑥 𝑦 = 𝐵
63, 5nfor 1507 . . 3 𝑥(𝑦 = 𝐴𝑦 = 𝐵)
76nfab 2224 . 2 𝑥{𝑦 ∣ (𝑦 = 𝐴𝑦 = 𝐵)}
81, 7nfcxfr 2217 1 𝑥{𝐴, 𝐵}
Colors of variables: wff set class
Syntax hints:  wo 662   = wceq 1285  {cab 2068  wnfc 2207  {cpr 3407
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2064
This theorem depends on definitions:  df-bi 115  df-tru 1288  df-nf 1391  df-sb 1687  df-clab 2069  df-cleq 2075  df-clel 2078  df-nfc 2209  df-v 2604  df-un 2978  df-sn 3412  df-pr 3413
This theorem is referenced by:  nfsn  3460  nfop  3594
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