How are the simplest anglesclassified?
Angles are usually expressed in terms of “rotation,” in which a full rotation is equal—
in most cases—to a 360 degree circle. Half of a full rotation is called a straight angle;
a quarter of a full rotation is called a right angle(90 degrees). An angle less than a
right angle is called an acute angle;an angle greater than a right angle is called an
obtuse angle.What are other types of angles?
There are numerous other types of angles, some of which are examined in the follow-
ing list:
Adjacent angle—Adjacent angles are two angles side-by-side that have a common ver-
tex (endpoint) and ray; angles are adjacent if a common line is between the other sides.
Vertical angles—Vertical angles are two angles whose sides form two pairs of
opposite rays; because of this, vertical angles have no sides in common and are direct-
ly across from one another. They are also considered a pair of opposite congruent
angles where two lines intersect. Vertical angles include intersecting lines that define
a plane, with the vertical angles always in the same plane.
Congruent angles—Congruent angles have the same size and shape; vertical
angles are considered to be congruent.
Exterior and interior angles—Interior angles are those inside a polygon, such as a
triangle; exterior angles are outside the polygon formed by extending one ray (side)
174 outside the polygon from a vertex.
The angles of a circle are typically measured either
in degrees or radians (rad). There are 360 degrees in
a circle, or 2π1 rad.The four basic types of angles are straight, acute,
obtuse, and right.