- Tim Brzezinski
A parabola can be defined as the set of points in a plane that are equidistant from a given point (the focus) and a fixed line (the directrix). Drag the black slider to illustrate this definition. You can move point P anywhere you'd like prior to doing so. In this figure, p = the directed distance from the vertex , to the focus . When p > 0 the focus and directrix are displayed in blue. When p < 0, these elements become red.
Developed for use with Thomas' Calculus, published by Pearson.