## Coordinate Geometry

### Cartesian plane

A  cartesian plane, named after the mathematician Rene Descartes, is a plane with a rectangular coordinate system that associates each point in the plane, with an ordered pair (x, y). The plane is called the cartesian plane, or the coordinate plane, or the xy-plane.

### Coordinate Axes

The coordinate plane has two mutually perpendicular axes which are number lines. The horizontal axis is called the x-axis. The vertical axis is called the y-axis. The point where both the axes intersect is called the origin.

The horizontal line XOX′ is the x-axis and the vertical line YOY′ is the y-axis. The origin is at zero division on the x-axis and zero division on the y-axis.The positive numbers are labelled on the directions OX and OY. So, OX and OY are called the positive directions of the x - axis and the y - axis, respectively. Similarly, negative numbers are labelled on the directions OX' and OY'. So,OX′ and OY′ are called the negative directions of the x - axis and the y - axis, respectively.