An ANGLE... a
is a set of points, all of which meet a stated condition.
b
is the set of all points in a plane equidistant from a given point, the center.
c
is any quantity that has size and direction; it can be represented as an arrow that starts at one point, the initial point, and points to a second, the terminal point.
d
comprises two rays with the same endpoint; the rays are the sides of the angle