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