*Macmillan Science Library: Mathematics*. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.

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## Understanding Three-Dimensional Coordinates

A two-dimensional coordinate system is formed by two **perpendicular** lines designated as an *x*-axis and a *y*-axis. The two lines meet at a point called the origin. With a three-dimensional coordinate system, a third axis line is added. The third axis line intersects the other two axis lines at the origin, forming right angles with each of them. The *x*-axis shows locations of points in space lying in front and back of the origin. The *y*-axis shows the location of points in space to the left and to the right of the origin. The *z*-axis shows points in space lying above and below the origin.

One way to visualize a three-dimensional coordinate system is to imagine yourself standing in a room near one of its corners, and facing the corner. The *x*-axis extends along the base of the...

This section contains 755 words(approx. 3 pages at 300 words per page) |