Vertical Section of Empty Set
Jump to navigation
Jump to search
Theorem
Let $X$ and $Y$ be sets.
Let $x \in X$.
Then:
- $\O_x = \O$
where $\O$ is the empty set and $\O_x$ is the $x$-vertical section of $\O$.
Proof
Aiming for a contradiction, suppose suppose that:
- $y \in \O_x$
Then from the definition of the $x$-vertical section, we have:
- $\tuple {x, y} \in \O$
This is impossible from the definition of the empty set.
So:
- there exists no $y \in \O_x$
giving:
- $\O_x = \O$
$\blacksquare$