Theorem csbconstgi

Description: The proper substitution of a class for a variable in another variable does not modify it, in inference form. (Contributed by Giovanni Mascellani, 30-May-2019)

	Ref	Expression
Hypothesis	csbconstgi.1	|- A e. _V
Assertion	csbconstgi	|- [_ A / x ]_ y = y

Proof

Step	Hyp	Ref	Expression
1		csbconstgi.1	|- A e. _V
2		csbconstg	|- ( A e. _V -> [_ A / x ]_ y = y )
3	1 2	ax-mp	|- [_ A / x ]_ y = y