/sci/ - Science & Math

>>11472007
I mean, you could be extremely formal, but it doesn't really matter.
For a), you'd have something like [math]f(f^{-1}(E)) = \{ f(x) \in \mathbb{Y} : x \in f^{-1} (E) \} = \{ f(x) \in \mathbb{Y} : x \in \mathbb{X} \wedge f(x) \in E \} \subset E[/math].