Theorem sbequ5

Description: Substitution does not change an identical variable specifier. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by NM, 15-May-1993) (New usage is discouraged.)

	Ref	Expression
Assertion	sbequ5	|- ( [ w / z ] A. x x = y <-> A. x x = y )

Proof

Step	Hyp	Ref	Expression
1		nfae	|- F/ z A. x x = y
2	1	sbf	|- ( [ w / z ] A. x x = y <-> A. x x = y )