Angles

Angles A shape formed by two rays sharing a

common endpoint; contains two rays and a vertex

ray

ray

vertexray—has one endpoint and goes infinitely in one direction

vertex—point common to two rays of a triangle or two sides of a polygon

Naming AnglesAn angle is named by three letters.

The vertex must be in center.

A

B C

1

Types of Angles Acute angle: An angle whose

measure is greater than zero degrees and less than 90 degrees

Which angles are not acute?1

23

4

5

Types of Angles Right angle: Angle that measures

90 degrees

Which angle is a right angle?1

23

4

5

Types of Angles Obtuse angle: One angle measures

greater than 90 degrees and less than 180 degrees

Which angle is an obtuse angle?1

23

4

5

Straight Angle Straight angle: A line that goes

infinitely in both directions and measures 180 degrees

Which is not a straight angle?

1 2

This is a ray. It only goes in one direction.

Adjacent angles are “side by side” and share a common ray.

45º15º

These are examples of adjacent angles.

55º

35º

50º130º

80º 45º

85º20º

These angles are NOT adjacent.

45º55º

50º100º

35º

35º

When 2 lines intersect, they make vertical angles.

75º

75º

105º105º

Vertical angles are opposite one another.

75º

75º

105º105º

Vertical angles are opposite one another.

75º

75º

105º105º

Vertical angles are congruent (equal).

30º150º

150º30º

Supplementary angles add up to 180º.

60º120º

40º

140º

Adjacent and Supplementary Angles

Supplementary Anglesbut not Adjacent

Complementary angles add up to 90º.

60º

30º40º

50º

Adjacent and Complementary Angles

Complementary Anglesbut not Adjacent

Practice Time!

Directions: Identify each pair of angles as vertical, supplementary, complementary, or none of the above.

#1

60º120º

#1

60º120º

Supplementary Angles

#2

75º75º

#2

75º75º

Vertical Angles

#3

65º

25º

#3

65º

25º

Complementary Angles

Directions:Determine the missing angle.

#1

45º?

#1

45º135º

#2

65º

?

#2

65º

25º

#3

35º

?

#3

35º

35º

#4

50º

?

#4

50º

130º