<P> In mathematics, a parabola is a plane curve, which is mirror - symmetrical, and is approximately U-shaped when oriented as shown in the diagram below (it remains a parabola if is differently oriented). It fits any of several superficially different mathematical descriptions, which can all be proved to define exactly the same curves . </P> <P> One description of a parabola involves a point (the focus) and a line (the directrix). The focus does not lie on the directrix . The parabola is the locus of points in that plane that are equidistant from both the directrix and the focus . Another description of a parabola is as a conic section, created from the intersection of a right circular conical surface and a plane which is parallel to another plane which is tangential to the conical surface . A third description is algebraic . A parabola is a graph of a quadratic function, y = x, for example . </P>

How to describe the shape of a parabola