Foci of an Ellipse, Conic Sections, Algebra II

The foci of an ellipse are explored in this video. First, foci are shown as the two points on the central axis such that the sum of the distance from a point on the ellipse and the foci points is the same as the distance from any point on the ellipse, and that distance is 2a, where a is the length of the central axis. Next, the distance from the center to the foci along the central axis (a) is shown to be the square root of a2-b2. Finally, an example is shown where one needs to graph and find the coordinates of the foci given an equation of an ellipse.