Angles are geometric figures formed by two rays having the same
endpoint. The two rays are called the sides of the angle, and
their common endpoint the vertex of the angle.
An angle is often denoted by the symbol Ð
, followed by a number, a letter or three letters. If an angle is
named using letters, the middle letter denotes the vertex of the
angle, while the other letters refer to points on the sides of
the angle; if there is only one letter, it then refers to the
vertex. The above angle can be referred to as
Ð 1, Ð B
or Ð ABC.
As the vertex B is the vertex of three different angles, the
notation
Ð B would be ambiguous. The
three-letter rule for naming angles would be appropriate here.
Thus, while Ð B is inexact in naming
the above angles, ÐABC , ÐABD,
ÐCBD each refer to a unique angle.
|
