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 A B C A C

Proof

Step Hyp Ref Expression
1 resss A B A
2 imass1 A B A A B C A C
3 1 2 ax-mp A B C A C