Angle Relationships

 $\overleftarrow{A}\overrightarrow{B}$  

 $\overline{AB}$  

 $\overrightarrow{AB}$  

 $\angle$ XYZ             m $\angle$  XYZ = $120\degree$  

 $\angle$ ZYX             m $\angle$  ZYX = $120\degree$  

Two angles are complementary if the sum (+) of the two angles = 90°.

Two angles are supplementary if the sum (+) of the two angles = 180°.

Take 60 seconds to jot down

two things you notice and

one thing you wonder.

Definitions:
Vertical angles are pairs of opposite angles that form when two lines meet at a point.
Congruent angles are angles that have the same measure.

Vertical angles:
  (1.) are congruent.
           $m\angle1\ \cong\ m\angle3$ 
           $m\angle4\ \cong\ m\angle2$    

 (2.) can be used to find the measure of supplemental angles.
           $m\angle1+m\angle2\ =\ 180\degree$ 
           $m\angle2+m\angle3\ =\ 180\degree$