The coordinate plane or Cartesian plane is a basic concept for coordinate geometry. It describes a two-dimensional plane in terms of two perpendicular lines or axes: x-axis and y-axis. The x-axis forms a horizontal number line while the y-axis forms a vertical number line. The x-axis and the y-axis meets at the point of origin.
The position of a point on the Cartesian plane is represented by a pair of numbers. The pair is called an ordered pair or coordinates (x, y). The first number, x, called the x-coordinate and the second number, y, is called the y-coordinate.
The origin is indicated by the ordered pair or coordinates (0, 0)
To get to the point (x, y), we start from the origin.
If x is positive then we move x units right from the origin otherwise if x is negative then we move x units left from the origin. Then, if y is positive, we move y units up otherwise if y is negative, we move y units down.
In the following coordinate plane: .
Point M has coordinates (2, 1.5). To get to point M, we move 2 units to the right (positive) and 1.5 units up (positive).
Point L is represented by the coordinates (–3, 1.5). To get to point L, we move 3 units to the left (negative) and 1.5 units up (positive)
Point N has coordinates (–2, –3). To get to point N, we move 2 units to the left (negative) and 3 units down (negative).
Notice that the x-axis and y-axis divide the Cartesian plane into 4 regions known as quadrants. They are labeled 1st, 2nd, 3rd and 4th quadrants accordingly in an anticlockwise direction.
Quadrant 1 contains positive x values and positive y values.
Quadrant 2 contains negative x values and positive y values.
Quadrant 3 contains negative x values and negative y values.
Quadrant 4 contains positive x values and negative y values.