Equation of a rectangle I need to graph a rectangle on the Cartesian coordinate system. Is there an equation for a rectangle? I can't find it anywhere. 

I found recently a new parametric form for a rectangle, that I did not know earlier: 
$$
\begin{align}
x(u) &= \frac{1}{2}\cdot w\cdot \mathrm{sgn}(\cos(u)),\\
y(u) &= \frac{1}{2}\cdot h\cdot \mathrm{sgn}(\sin(u)),\quad  (0 \leq u \leq 2\pi)
\end{align}
$$
where $w$ is the width of the rectangle and $h$ is its height.  
I have used this in modelling parametric ruled surfaces, where it seems to be rather handy.
