Daily Printable Equation Collection

This thing collects together all of my printable equations (see http://www.thingiverse.com/tag:Daily_Equation). For more detail and photos of each equation, see individual things. To just see each new equation as I post it, put a watch this thing.
I've always been interested in different ways to visualize and explore data. I thought it would be cool to try to print 3d representations of equations. The graphing libraries I could find weren't flexible enough for what I needed, so I wrote a Python program to take an equation and plot it in Openscad using the polygon command. The 3d equation is mounted on a stand that also displays the text form of the equation (write.scad used for text).
I'm going to post one equation per day until get bored or people lose interest. If there's a particular equation you'd like to see, leave a comment and I'll give it a shot.
Day 1 - y = a*sin(b*x)
(http://www.thingiverse.com/thing:227223)
Day 2 - x^(2/3) + y^(2/3) = a
(http://www.thingivers