Area of Square

Theorem
A square has an area of $L^2$ where $L$ is the length of a side of the square.

Thus we have that the area is a function of the length of the side:
 * $\forall L \in \R_{\ge 0}: \map \Area L = L^2$

where it is noted that the domain of $L$ is the set of non-negative real numbers.