\begin{definition}[Definition:Constructible Point in Plane]
Let $\CC$ be a Cartesian coordinate plane.
Let $S$ be a set of points in $\CC$.
Let $P$ be a point in $\CC$.
Let there exist a compass and straightedge construction for $P$ from a line segment $AB$, where $A, B \in S$
Then $P$ is defined as '''constructible from $S$'''.
\end{definition}