Sometimes it is useful in mathematics to describe the path that a point traces as it moves in a plane to meet certain conditions. For example, what is the path that a point on the end of the second hand of a clock traces in 60 seconds? This answer, of course, is a circle.

One way to define a circle is to say that a circle is the locus of all the points in a plane that are a given distance from a fixed point, called the center.

A locus in a plane can be thought of as all the possible locations or positions that a point can take as it moves to meet certain stated conditions. What is the locus of, or path traced by, a point in a plane that moves so that it is always three inches from point A? This locus will be a circle...