Theorem fimassd

Description: The image of a class is a subset of its codomain. (Contributed by Glauco Siliprandi, 23-Oct-2021)

	Ref	Expression
Hypothesis	fimassd.1	$$⊢\phi \to F:A⟶B$$
Assertion	fimassd	$$⊢\phi \to F\left[X\right]\subseteq B$$

Proof

Step	Hyp	Ref	Expression
1		fimassd.1	$$⊢\phi \to F:A⟶B$$
2		fimass	$$⊢F:A⟶B\to F\left[X\right]\subseteq B$$
3	1 2	syl	$$⊢\phi \to F\left[X\right]\subseteq B$$