The Best Explanation of the Equation of an Ellipse

I made this with a lot of heart, and every purchase helps me keep creating. If you like what I do or just want to support independent makers, check it out: http://amazon.com/gp/product/B093D22DGN Thank you for being here—it really means a lot. In this video we derive the equation of an ellipse. An ellipse is defined as the locus of all points in the plane for which the sum of the distances r1 and r2 to two fixed points F1 and F2 (called the foci) separated by a distance 2c, is a given constant 2a. Therefore, from this definition the equation of the ellipse is: r1 + r2 = 2a, where a = semi-major axis.