The Rectangular Coordinate Plane (1)
The point of intersection of the x- and y-axes is called the origin. The coordinate 0 of each axis is at the origin.
Every point on the plane is associated with a unique ordered pair of real numbers. To illustrate this, let P be any point on the plane. Draw a vertical line and a horizontal line through point P, as shown in the figure below.
As you can see in the figure, the vertical line intersects the x-axis at a unique point. Similarly, the horizontal line intersects the y-axis at a unique point.
The numbers a and b that correspond to these points on the x- and y-axes, respectively, form the ordered pair Such ordered pair gives the coordinates of point P. You call a the x-coordinate (or abscissa) of P, and b the y-coordinate (or ordinate) of P.
