Lesson 1: Angles and Angle Classification
Angles A shape formed by two rays sharing a common endpoint; contains two rays and a vertex 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
Naming Angles An angle is named by three letters. The vertex must be in center. A 1 B C
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 2 3 4 5
Types of Angles Right angle: Angle that measures 90 degrees Which angle is a right angle? 1 2 3 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 2 3 4 5
This is a ray. It only goes in one direction. Straight Angle Straight angle: A line that goes infinitely in both directions and measures 180 degrees Which is not a straight angle? 2 1 This is a ray. It only goes in one direction.
Adjacent angles are “side by side” and share a common ray. 15º 45º
These are examples of adjacent angles. 45º 80º 35º 55º 130º 50º 85º 20º
These angles are NOT adjacent. 100º 50º 35º 35º 55º 45º
When 2 lines intersect, they make vertical angles. 75º 105º 105º 75º
Vertical angles are opposite one another. 75º 105º 105º 75º
Vertical angles are opposite one another. 75º 105º 105º 75º
Vertical angles are congruent (equal). 150º 30º 150º 30º
Supplementary angles add up to 180º. 40º 120º 60º 140º Adjacent and Supplementary Angles Supplementary Angles but not Adjacent
Complementary angles add up to 90º. 30º 40º 50º 60º Adjacent and Complementary Angles 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 75º
#2 Vertical Angles 75º 75º
#3 25º 65º
#3 25º 65º Complementary Angles
Directions: Determine the missing angle.
#1 ? 45º
#1 135º 45º
#2 ? 65º
#2 25º 65º
#3 ? 35º
#3 35º 35º
#4 ? 50º
#4 130º 50º