Answer: A hyperbola is the set of points in a plane the difference of whose distances from
two fixed points, called foci, is constant.
Step-by-step explanation: 4 illustrates the two branches of a hyperbola. The line through the
foci intersects the hyperbola at two points, called the vertices. The line segment that
joins the vertices is the transverse axis. The midpoint of the transverse axis is the
center of the hyperbola. Notice that the center lies midway between the vertices, as
well as midway between the foci.
