This page uses **JavaSketchpad**, a World-Wide-Web component of *The Geometer's Sketchpad.* Copyright © 1990-2001 by KCP Technologies, Inc. Licensed only for non-commercial use.

####

Parabola

This sketch confirms an ancient definition of a parabola as the locus of a point that has equal distances from a given point and line. Here, the given point is *F* and the given line is *AB*. Printed measurements confirm the equality of distances. A proof follows from the fact that the triangle *FXY* is isosceles.
For more, see **GEOMETRY IN ACTION**, Chapter 3.