Metamath Proof Explorer


Theorem resimass

Description: The image of a restriction is a subset of the original image. (Contributed by Glauco Siliprandi, 23-Oct-2021)

Ref Expression
Assertion resimass ABCAC

Proof

Step Hyp Ref Expression
1 resss ABA
2 imass1 ABAABCAC
3 1 2 ax-mp ABCAC