For example, when the three lines A B, A C, and A D in [fig. 37] meet in the common point A, we designate either of the angles formed, by three letters, placing that at the vertex between those at the opposite extremities of the including lines. Thus, we say, the angle B A C, etc.
APEX.—The summit or highest point of an object.
ARC.—See [circle].
AXIS OF A SOLID.—An imaginary straight line passing through its center.
AXIS OF A FIGURE.—A straight line passing through the center of a figure, and dividing it into two equal parts.
BASE.—The base of a solid figure is that on which it stands—the lowest part.
BISECT.—To divide into two equal parts.
BISECTOR.—A line which bisects.
Fig. 38.