# Parabola

The English used in this article may not be easy for everybody to understand. |

The **parabola** (from the Greek παραβολή) is a type of curve. Menaechmus (380–320 BC) discovered the parabola, and Apollonius of Perga (262 BC–c190 BC) first named it.

A parabola is a conic section. If a cone is dissected by a plane which is parallel to one of the surfaces of the cone, the result is a parabola. The point where the parabola reaches its maximum or minimum is called the "vertex." At this point the curvature of the parabola is greatest.

Each parabola has a focal point. Any ray that enters the parabola and is parallel to the axis of symmetry will pass through this point after being reflected by the curve. Because of this fact, parabolas are important in devices such as satellite dishes, or magnifying mirrors. Parabolas are often used to approximate curves that are more difficult to model by themselves.

Every parabola uses the equation <math>y = ax^2 + bx + c</math>, where <math>a</math>, <math>b</math> and <math>c</math> are constants, and <math>a</math> is not equal to <math>0</math>.

- Bouncing ball strobe edit.jpg
The bouncing of a ball will be parabolic, if friction is neglected

- ParabolicWaterTrajectory.jpg
The course of the water in a fountain is parabolic

- St Louis Gateway Arch.jpg
The Gateway Arch in St. Louis looks like it is shaped like a parabola, but it is actually an inverted weighted catenary

- Offset Schotelantenne.jpg
A satellite receiver is shaped like a parabola