A locus is a set of points that contains all the points, and only the points, that satisfy the condition, or conditions, required to describe a geometric figure. The word locus is Latin for place or location. A locus may also be defined as the path traced out by a point in motion, as it moves according to a stated set of conditions, since all the points on the path satisfy the stated conditions. Thus, the phrases "locus of a point" and "locus of points" are often interchangeable. A locus may be rather simple and appear to be obvious from the stated condition. Examples of loci (plural for locus) include points, lines, and surfaces. The locus of points in a plane that are equidistant from two given points is the straight line that is perpendicular to and passes through the center of the line segment connecting the two...