This is Day 12 of my collection of printable equations. To see the whole collection, go to:http://www.thingiverse.com/thing:227210
Things are a little hectic this week, so I decided to go with something simple, an ellipse (http://en.wikipedia.org/wiki/Ellipse). The equation is a variant of the circle (Day 8, x^2 + y^2 = a http://www.thingiverse.com/thing:233659), but with different divisors for x and y. So, x^2/a + y^2/b = 1. A and b control the maximum/minimum in the x and y direction, respectively.
As always, I'm going to continue 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.