Coordinate Geometry class 9 – Two perpendicular lines, one horizontal line and the other vertical line is required for locating a point or an object in a plane. These perpendicular lines are called the coordinate Axes and the plane is called the coordinate plane also known as Cartesian plane. The horizontal and vertical lines are called x axis and y axis respectively. These x and y coordinate axes divides the cartesian plane into 4 identical parts known as quadrants and the point of intersection of x and y axes is called origin, generally denoted by ‘o’. The distance between y axis and any point in a plane is called its x coordinate, also known as abscissa. Similarly, the distance between x axis and any point in a plane is called its y coordinate, also known as ordinate. If x and y are the abscissa and the ordinate of a point Q, then, (x, y) are called the coordinates of point Q. The general form of coordinates of a point on the x-axis are (x, 0) and that of the point on the y-axis are (0, y).
The coordinates of the origin ‘o’ are (0, 0). If a positive real number is denoted by ‘+’ and a negative real number is denoted by ‘-’, then, the sign convention of coordinates in 1st quadrant is (+ , +), In 2nd quadrant (–, +), in 3rd quadrant (–, –), and in the fourth quadrant (+, –).
Also, If x is not equal to y, then the values (x, y) will not be equal to (y, x). The coordinates (x, y) and (y, x) are equal if, x = y.
Coordinate Geometry class 9 Examples