The

horizonis the "apparent junction of earth and sky."The following is a number line written

horizontally.<--+---+---+---+---+---+---+---+---+---+---+--> -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5The

verticalis "perpendicularto the plane of the horizon or to a primary axis." [Perpendicularis "being at right angles to a given line or plane."]The following is a number line written vertically.

^ | +5 + | +4 + | +3 + | +2 + | +1 + | 0 + | -1 + | -2 + | -3 + | -4 + | -5 + | v## Right Angle

Perpendicular lines intersect and their point of intersection is called the

origin. Perpendicular lines form four right angles at the origin. A right angle measures ninety degrees (`90°`

).With respect the

Cartesian coordinate system, the horizonal line is the`x-axis`

and the vertical line is the`y-axis`

.| <-- vertical-axis (y-axis) | | | --------o-------- <-- horizonal-axis (x-axis) |\ | \ | o is the origin |Note: The Cartesian coordinate system was developed by French mathematician and philosopher Rene Descartes in approximately 1637.

RoadHacker:: Horizon/Vertical Slideshow [opens new window]

**Creator:** Gerald Thurman
[gthurman@gmail.com]

**Created:** 09 February 2005

**Last Modified:** Saturday, 05-Jan-2013 11:18:13 MST

This work is licensed under a Creative Commons Attribution 3.0 United States License.