__CHAPTER 3 COORDINATE GEOMETRY__

- To locate the position of an object or a point in a plane, we require two perpendicular l One of them is horizontal, and the other is vertical.

- The plane is called the Cartesian, or coordinate plane and the lines are called the coordinate axes.

- The horizontal line is called the
*x*-axis, and the vertical line is called the*y*– axis.

- The coordinate axes divide the plane into four parts called quadrants.

- The point of intersection of the axes is called the origin.

- The distance of a point from the
*y*– axis is called its*x*-coordinate, or abscissa, and the distance of the point from the*x*-axis is called its*y*-coordinate, or ordinate.

- If the abscissa of a point is
*x*and the ordinate is*y*, then (*x*,*y*) are called the coordinates of the point.

- The coordinates of a point on the
*x*-axis are of the form (*x*, 0) and that of the point on the*y*-axis are (0,*y*).

- The coordinates of the origin are (0, 0).

- The coordinates of a point are of the form (+, +) in the first quadrant, (–, +) in the second quadrant, (–, –) in the third quadrant and (+, –) in the fourth quadrant, where + denotes a positive real number and – denotes a negative real number.

- If
*x≠ y*, then (*x*,*y*) ≠ (*y*,*x*), and (*x*,*y*) = (*y*,*x*), if*x*=*y*