16-10-2010, 03:55 PM
[attachment=6307]
INTRODUCTION
The parabola is the locus of all points in a plane that are the same distance from a line in the plane, the directrix, as from a fixed point in the plane, the focus.
The parabola has one axis of symmetry, which intersects the parabola at its vertex
The distance from the vertex to the focus is | p |.
The distance from the directrix to the vertex is also | p |.