The points lying on a vertical line share the same [tex]x[/tex] coordinate. Similarly, the points lying on a horizontal line share the same [tex]y[/tex] coordinate.
So, vertical lines are identified by the [tex]x[/tex] coordinate of their points, and have an equation like [tex]x=x_0[/tex], where [tex]x_0[/tex] is a fixed real number.
Similarly, horizontal lines are identified by the [tex]y[/tex] coordinate of their points, and have an equation like [tex]y=y_0[/tex], where [tex]y_0[/tex] is a fixed real number.
We are ready to answer the questions:
- A vertical line passing through the point (2, -4) has equation [tex]x=2[/tex]
- A horizontal line passing through the point (2, -4) has equation [tex]y=-4[/tex]
- The two lines are perpendicular
