http://www.askamathematician.com/2010/12/q-what-does-00-zero-raised-to-the-zeroth-power-equal-why-do-mathematicians-and-high-school-teachers-disagree/
Plot of z = xy. The red curves (with z constant) yield different limits as (x,y) approaches (0,0). The green curves (of finite constant slope, y = ax) all yield a limit of 1.
From https://en.wikipedia.org/wiki/Exponentiation
