4.1 Angles Formed by Intersecting Lines

4.1 Angles Formed by Intersecting Lines

Adjacent Angles

Non-overlapping angles that share a vertex and share a side.

 $\angle PQS$  and  $\angle RQS$  are adjacent angles. They share the vertex Q and the side  $\overrightarrow{QS}$  

Complementary Angles

Angles that add up to  $90\degree$  

(The right angle box indicates  $\angle FGM$  and  $\angle KGM$  are complementary)

Supplementary Angles

Angles that add up to $180\degree$  

Linear Pair

 $m\angle KJM+m\angle LJM=180$  

A pair of adjacent angles that form a straight line. Linear pairs are always supplementary.

Vertical Angles

When two lines intersect, vertical angles are the angles that are opposite each other.
Vertical angles are always congruent.

 $\angle AEB\cong\angle DEC$  and  $\angle AED\cong\angle BEC$