# Parabola: Standard Equation of Parabola and Parabola Equation Derivation (For CBSE, ICSE, IAS, NET, NRA 2022)

Doorsteptutor material for competitive exams is prepared by world's top subject experts: get questions, notes, tests, video lectures and more- for all subjects of your exam.

# Title: Parabola

- A parabola is a U-shaped plane curve where any point is at an equal distance from a fixed point (known as the focus) and from a fixed straight line which is known as the Directrix
- A parabola, plural “parabolas;” Gray 1997, S the set of all points in the plane equidistant from a given line L (the conic section directrix) and a given point F not on the line (the focus) .
- Focal parameter (i.e.. , the distance between the directrix and focus) is therefore given by 2-a, where a is the distance from the vertex to the directrix or focus. The surface of revolution obtained by rotating a parabola about its axis of symmetry is called a paraboloid.
- Parabola is an integral part of conic section topic and its entire concepts parabola are covered here.

## What is Parabola?

- Section of a right circular cone by a plane parallel to a generator of the cone is a
**parabola**. - It is a locus of a point, which moves so that distance from a fixed point (focus) is equal to the distance from a fixed line (Directrix)
- Fixed point is called focus
- Fixed line is called Directrix

## Standard Equation of Parabola

- The simplest equation of a parabola is when the directrix is parallel to the y-axis.
- Generally, if the directrix is parallel to the y-axis in the standard equation of a parabola is given as:
- If the parabola is sideways i.e.. , the directrix is parallel to x-axis, the standard equation of a parabola becomes,
- Apart from these two, the equation of a parabola can also be and if the parabola is in the negative quadrants.
- Thus, the four equations of a parabola are given as:

## Parabola Equation Derivation

- Three points uniquely determine one parabola with directrix parallel to the x-axis and one with directrix parallel to the y-axis.
- If these parabolas pass through the three points , they are given by equations

and

## Parabola Equations

In polar coordinates, the equation of a parabola with parameter and center (0,0) is given by