Two angles and , with a common side
, are
if belongs to the interior of .
The sum of angles on a straight line is , and two such angles are called a linear pair. Two angles are called
supplementary if the sum of their measures is
their measures is
; two angles are called complementary if the sum of
. Describing angles as supplementary or complementary refers only to the
measures of their angles. The positions of the angles or whether the pair of angles is adjacent to each other is not part
of the definition.
