1. Lesson 1-5
Pairs of Angles

2. Complementary Angles Definition: A pair of angles whose sum is 90˚
Examples:
Adjacent Angles
( a common side )
Non-Adjacent Angles

3. Supplementary Angles Definition: A pair of angles whose sum is 180˚
Examples:
If they are adjacent
then they are also called
a “Linear Pair” of angles.
Non-Adjacent Angles

4. Vertical Angles Definition:
A pair of angles whose sides form opposite rays.
Examples:

5. Theorem: Vertical Angles are =~
Given:
The diagram
Prove:
statements
reasons 1. 1.
Definition: Linear Pair 2. 2.
Property: Substitution 3. 3.
Property: Subtraction 4. 4.
Definition: Congruence

6. What’s “Important” in Geometry?
4 things to always look for !
180˚
90˚
360˚
Most of the rules (theorems)
and vocabulary of Geometry
are based on these 4 things.
. . . and Congruence

7. ( ) = ( ) ( ) + ( ) = ( ) ( ) + ( ) = 90˚ ( ) + ( ) = 180˚
Algebra and Geometry
Common Algebraic Equations used in Geometry:
( ) = ( )
( ) + ( ) = ( )
( ) + ( ) = 90˚
( ) + ( ) = 180˚
If the problem you’re working on has a variable (x),
then consider using one of these equations.