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Metamath Proof Explorer

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	$⊢ A \in V$
	Assertion	csbconstgi	$⊢ ⦋ A / x ⦌ y = y$

Proof

Step	Hyp	Ref	Expression
1		csbconstgi.1	$⊢ A \in V$
2		csbconstg	$⊢ A \in V \to ⦋ A / x ⦌ y = y$
3	1 2	ax-mp	$⊢ ⦋ A / x ⦌ y = y$