Lesson 1 Angles and Angle Classification Angles o

Lesson 1: Angles and Angle Classification

Angles o A shape formed by two rays sharing a common endpoint; contains two rays and a vertex—point common to two rays of a triangle or two sides of a polygon ray vertex ray—has one endpoint and goes infinitely in one direction ray

Naming Angles o. An angle is named by three letters. The vertex must be in center. A 1 B C

Types of Angles o Acute angle: An angle whose measure is greater than zero degrees and less than 90 degrees Which angles are not acute? 4 1 3 2 5

Types of Angles o Right angle: Angle that measures 90 degrees Which angle is a right angle? 4 1 3 2 5

Types of Angles o Obtuse angle: One angle measures greater than 90 degrees and less than 180 degrees Which angle is an obtuse angle? 4 1 3 2 5

Straight Angle o 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. 45º 15º

These are examples of adjacent angles. 80º 45º 35º 55º 85º 130º 20º 50º

These angles are NOT adjacent. 100º 50º 35º 55º 45º

When 2 lines intersect, they make vertical angles. 75º 105º 75º

Vertical angles are opposite one another. 75º 105º 75º

Vertical angles are opposite one another. 75º 105º 75º

Vertical angles are congruent (equal). 150º 30º 150º

Supplementary angles add up to 180º. 40º 120º 60º Adjacent and Supplementary Angles 140º Supplementary Angles but not Adjacent

Complementary angles add up to 90º. 30º 40º 60º Adjacent and Complementary Angles 50º Complementary Angles but not Adjacent

Practice Time!

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

#1 120º 60º

#1 120º 60º Supplementary Angles

#2 75º

#2 Vertical Angles 75º

#3 25º 65º

#3 25º 65º Complementary Angles

Directions: Determine the missing angle.

#1 135º 45º

#2 25º 65º

#3 35º

#4 130º 50º