We know that the position of a point in a plane is given by its coordinates.
In the adjoining figure, XOX’ and YOY’ are two intersecting and mutually perpendicular straight lines. Together, the two lines form the frame of reference in the Cartesian x-y plane for which
(i) XOX’ is called the x-axis.
(ii) YOY’ is called the y-axis, and
(iii) O is called the origin.
The x-axis and the y-axis divide the x-y plane into four parts, called quadrants, as shown in the figure.
A is the point in the first quadrant whose distance from the y-axis and x-axis are 3 and 4 units respectively. So, the coordinates of A are (3, 4). We express it by writing A = (3, 4). B, C and D are also points whose distance from the y-axis and the x-axis are same as those of point A. But due to their positions in different quadrants, their coordinates are different. Thus, the coordinates of B, in the second quadrant, are (-3, 4); those of C, in the third quadrant, are (-3, -4) and those of D, in the fourth quadrant, are (3, -4)