Definition:Image (Relation Theory)/Mapping/Subclass
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Definition
Let $V$ be a basic universe.
Let $A \subseteq V$ and $B \subseteq V$ be classes.
Let $f: A \to B$ be a class mapping.
Let $C \subseteq A$.
The image of $C$ under $f$ is defined as:
\(\ds f \sqbrk C\) | \(=\) | \(\ds \set {y \in B: \exists x \in C: \map f x = y}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds \set {\map f x: x \in C}\) |
That is, it is the class of all $y$ such that $\tuple {x, y} \in f$ for at least one $x \in C$.
Also see
- Results about images can be found here.