To get the equation of a conic in terms of and , we use a property, known as the **focus-directrix property**.

Let there be a fixed line (The **Directrix**) and a fixed point (The **Focus**). Let be a point on the locus of conic and let be perpendicular to . Clearly, as moves, slides on . Now, consider the ratio

If we do not allow this ratio to change, 4 possibilities arise, giving us distinct shapes:

**Axis** of a conic is the line about which a conic is symmetric. A conic may have 1 or 2 or more axes of symmetry.

**Vertex** of a conic is the point of intersection of the conic with the axis.

**Chord** is any line segment, which joins 2 points on a curve. If the chord passes through the **focus**, it is known as **focal chord**.

**Focal length** is the length of segment which joins a point on the conic to the focus.

**Latus rectum** is the focal chord which is perpendicular to the axis.

**Center** of a conic is the point which bisects every chord of the conic passing through it.

**Double ordinate** of a conic is any chord, which is perpendicular to the axis.

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