In coordinate
geometry the term 'x-axis'
usually refers to a horizontal number line. This number line has values increasing
toward the right. That is, positive values become greater as one moves down the x-axis from zero,
the origin, toward the right, and negative values become less as
one moves left from zero. This is
shown on the following diagram.
The x-axis extends to negative infinity on the left and to positive infinity
to the right.
A point on the x-axis has both a coordinate and a
name. The coordinate is the value on the number
line where the point is located. The name is usually a letter. Here we will
use the name 'x' for a point on the x-axis. The name of the point can be
used in equations to represent the numeric value of the coordinate, as in
x = 2.
The point with the name of 'x' has a coordinate value of 2.
The above is a picture of how we will often present points in diagrams, but
actually points are really much smaller than this. In fact, points are so
small that they do not even have a size. Points have no dimension. They have
no width or height; they are just a location. Well, that lack of dimension
often makes the points difficult to see in diagrams. So, we use these little
yellow disks, or similar devices, to visibly and clearly mark off the
location of our points.
In coordinate
geometry the term 'x-axis'
usually refers to a horizontal number line. This number line has values increasing
toward the right. That is, positive values become greater as one moves down the x-axis from zero,
the origin, toward the right, and negative values become less as
one moves left from zero. This is
shown on the following diagram.
