Theorem nfequid 1590

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.)

Assertion

Ref	Expression
nfequid	|- F/ y x = x

Proof of Theorem nfequid

Step	Hyp	Ref	Expression
1		equid 1589	. 2 |- x = x
2	1	nfth 1353	1 |- F/ y x = x

Syntax hints:   F/wnf 1349

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-gen 1338  ax-ie2 1383  ax-8 1395  ax-17 1419  ax-i9 1423

This theorem depends on definitions:  df-bi 110  df-nf 1350

This theorem is referenced by: (None)