Chapter 12: Basics of Geometry 157Two angles whose measurements total to 180r are called supplementary angles. If two angles are
supplementary, each is the supplement of the other.
DEFINITION
Complementary angles are a pair of angles whose measurements total 90r.
Supplementary angles are a pair of angles whose measurements total 180r.To find the supplement of an angle of 132r, 180r – 132r = 48r. The measure of the supplement of
an angle of 103r is 180 – 103 = 77r.
When two lines intersect, the lines make an X and four angles are formed. Each pair of angles
across the X from one another is a pair of vertical angles. Vertical angles are always congruent; they
always have the same measurement.
The angles AED and CEB are vertical angles, as are the angles DEC and AEB.Two angles that have the same vertex and share a side but don’t overlap are called adjacent angles.
Two adjacent angles whose exterior sides (the ones they don’t share) make a line are called a
linear pair. Linear pairs are always supplementary.
DEFINITION
Vertical angles are a pair of angles both of which have their vertices at the point where
two lines intersect and do not share a side.
Adjacent angles are a pair of angles that have the same vertex and share a side but do
not overlap one another.
A linear pair is made up of two adjacent angles whose unshared sides form a straight
angle.DE
BCA