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Theorem nfabd 3004
 Description: Bound-variable hypothesis builder for a class abstraction. Usage of this theorem is discouraged because it depends on ax-13 2392. Use the weaker nfabdw 3003 when possible. (Contributed by Mario Carneiro, 8-Oct-2016.) Avoid ax-9 2125 and ax-ext 2796. (Revised by Wolf Lammen, 23-May-2023.) (New usage is discouraged.)
Hypotheses
Ref Expression
nfabd.1 𝑦𝜑
nfabd.2 (𝜑 → Ⅎ𝑥𝜓)
Assertion
Ref Expression
nfabd (𝜑𝑥{𝑦𝜓})

Proof of Theorem nfabd
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 nfv 1916 . 2 𝑧𝜑
2 df-clab 2803 . . 3 (𝑧 ∈ {𝑦𝜓} ↔ [𝑧 / 𝑦]𝜓)
3 nfabd.1 . . . 4 𝑦𝜑
4 nfabd.2 . . . 4 (𝜑 → Ⅎ𝑥𝜓)
53, 4nfsbd 2566 . . 3 (𝜑 → Ⅎ𝑥[𝑧 / 𝑦]𝜓)
62, 5nfxfrd 1855 . 2 (𝜑 → Ⅎ𝑥 𝑧 ∈ {𝑦𝜓})
71, 6nfcd 2970 1 (𝜑𝑥{𝑦𝜓})
 Colors of variables: wff setvar class Syntax hints:   → wi 4  Ⅎwnf 1785  [wsb 2070   ∈ wcel 2115  {cab 2802  Ⅎwnfc 2962 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1971  ax-7 2016  ax-10 2146  ax-11 2162  ax-12 2179  ax-13 2392 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2071  df-clab 2803  df-nfc 2964 This theorem is referenced by:  nfabd2  3005  nfsbcd  3782  nfcsbd  3891  nfiotad  6307  nfiundg  45135
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