Daily Equation #8 - Circle - x^2 + y^2 = a

This is Day 8 of my collection of printable equations. To see the whole collection, go to: http://www.thingiverse.com/thing:227210

For today's equation, I'm continuing the series of equations of the form |x^b + y^c| = a (See days 2, 6, and 7). Previously, we saw that as b and c went from 1, the quadrants of the shape went from bending inward, to straight, to bowing out. As b,c --> 2, the quadrants continue to bow out until they form a perfect circle, and today's equation: x^2 + y^2 = a. You c