Theorem mpteq1iOLD

Description: An equality theorem for the maps-to notation. (Contributed by Glauco Siliprandi, 17-Aug-2020) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	mpteq1i.1	|- A = B
Assertion	mpteq1iOLD	|- ( x e. A |-> C ) = ( x e. B |-> C )

Proof

Step	Hyp	Ref	Expression
1		mpteq1i.1	|- A = B
2		mpteq1	|- ( A = B -> ( x e. A |-> C ) = ( x e. B |-> C ) )
3	1 2	ax-mp	|- ( x e. A |-> C ) = ( x e. B |-> C )