**Angle Definitions**

formed by two rays that share a

common endpoint.

**Angle:**

C

A

B

common endpoint of the two rays

Vertex of an Angle:

C

B

A

Point C is the vertex

Two rays

**Sides:**

C

B

A

CA and CB are sides.

**smallest amount of rotations**

about the vertex from one ray to another measured in degrees

about the vertex from one ray to another measured in degrees

Measure of an Angle:

**unit of measure for angles**

**Degree:**

geometry tool you use

to measure an angle

**Protractor:**

A ray that contains a vertex

and divides the angle into

two congruent angles

Angle Bisector:

C

B

A

angles that have the

same measure

Congruent Angles:

C

B

A

Z

X

Y

an example that shows a

definition or conjecture is

incorrect or incomplete

Counterexample:

coplanar lines that never intersect

Parallel Lines:

a

noncoplanar lines

Skew Lines:

an angle that is 90°

Right Angle:

an angle that is less than 90°

Acute Angle:

60°

an angle that is more than 90°

Obtuse Angle:

120°

Two lines that intersect at a 90° angle

Perpendicular Lines:

90°

Two coplanar angles that share

a common vertex and side

and no other points

Adjacent Angles:

1

2

Two angles that add up to 90°

Complementary Angles:

Two angles that add up to 180°

Supplementary Angles:

Two nonadjacent

angles formed by

intersecting lines

Vertical Angles:

1

2

Linear Pair:

**Two adjacent angles**

that are formed by

a line and ray

intersecting

that are formed by

a line and ray

intersecting

1. point on ray-vertex- point on another ray

Three Ways to Name an Angle:

2. Vertex

S

A

M

SAM

3. By a number

A

1

1

b

)

)

70

110

o

o