Introduction to AnglesComplementary and Supplementary

Lines, Rays, and Angles

A line goes forever in both directions.It is perfectly straight, and never ends.

A ray goes forever in one direction. It has one endpoint.

An angle is two rays that share an endpoint.

Parts of an Angle• The point where the rays intersect is

called the vertex of the angle.

• The two rays are called the sides of the angle.

Naming Angles• Use the vertex and a point from each ray to

name the angle. The vertex must be the middle letter. A

B C

Sometimes we put this symbol in front of an angle:

ABC

CBA

Vertexes and Sides

                          

Complementary Angles• Two angles are called complementary angles

if the sum (add) of their degree measurements equals 90 degrees.

• Complementary Angles make a Right Angle.

Example:Complementary Angles

Supplementary Angles

• Two angles are called supplementary angles if the sum of their degree measurements equals 180 degrees.

• Supplemental Angles make a Straight Line.

Example:Supplementary Angles

Find the complementary and supplementary angles for each.Use half sheet of paper.

1) 73 2) 40 3) 29

2) 87 5) 56 6) 13