Parabola

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A parabola
A parabola obtained as the intersection of a cone with a plane parallel to a straight line on its surface.
Parts of a parabola

The parabola (from the Greek παραβολή) is a type of regular curve. It is a conic section. If a cone is dissected by a line which is parallel to one of the surfaces of the cone, the result is a parabola. The point on the axis of symmetry that intersects the parabola is called its "vertex". At this point, the curvature of the parabola is greatest.

Menaechmus (380–320 BC) discovered the parabola, Apollonius of Perga first named it. Each parabola has a focal point. Rays that enter the parabola and that are parallel to its axis are focused on this point. Because of this fact, parabolas are important in everyday life: Devices such as satellite dishes, or mirrors use this property. Parabolas are are often used to approximate other curves, which are more difficult to model.

Every parabola obeys the equation f(x)=ax²+bx+c, where a,b and c are numbers, and a is not 0.

This parabola is not asymptotic to any line besides its directrix.