What Are Loci in Geometry?
A locus is a set of points that satisfies a specified condition. Here are some loci you need to know:
All points on a circle have the same distance from its center point.
The sum of the distances to the two focal points is the same for all points on the ellipse.
All points that are equidistant from two specified points.
All points equidistant to a specified straight line.
All points equidistant to two specified lines.
Every angle that spans a line segment. Added together, these angles create a circle.
On exams, you may be asked what locus is being described. For that reason, it will be useful to remember what defines the different loci.