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Theorem nfequid 1938
Description: Bound-variable hypothesis builder for 𝑥 = 𝑥. This theorem tells us that any variable, including 𝑥, is effectively not free in 𝑥 = 𝑥, even though 𝑥 is technically free according to the traditional definition of free variable. (Contributed by NM, 13-Jan-2011.) (Revised by NM, 21-Aug-2017.)
Ref Expression
nfequid 𝑦 𝑥 = 𝑥

Proof of Theorem nfequid
StepHypRef Expression
1 equid 1937 . 2 𝑥 = 𝑥
21nfth 1725 1 𝑦 𝑥 = 𝑥
Colors of variables: wff setvar class
Syntax hints:  wnf 1706
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1720  ax-4 1735  ax-5 1837  ax-6 1886  ax-7 1933
This theorem depends on definitions:  df-bi 197  df-ex 1703  df-nf 1708
This theorem is referenced by: (None)
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