Transparency 2 Review: Lesson 1-3 Mini-Quiz

Class Greeting

Objective: The students will learn how to measure angles and how to classify them according to the angle.

Chapter 1 – Lesson 4 Angle Measure

Vocabulary Degree The unit used to measure angles is the degree One degree is 1/360 th of a circle

Vocabulary Ray A ray is part of a line. It has one endpoint and extends forever in one direction. PQ

Naming Rays The name of a ray shows the endpoint first and then any other point on the ray This ray is PQ (not QP!) P Q

Angles an angle is formed by two non-collinear rays with the same endpoint the rays are called the sides of the angle the endpoint of the rays is the vertex of the angle

Angles

Opposite Rays A point on a line is the endpoint of two rays on that line called opposite rays Here the opposite rays are QP and QR P Q R Two rays with a common endpoint that form a 180 degree angle are called Opposite Rays. A 180 degree angle is called a Straight Angle.

Angles Divide the Plane An angle in a plane divides it into 3 parts: –Points on the angle –Points in the interior of the angle –Points in the exterior of the angle Points A,D & E are on the angle Points C & B are in the interior of the angle Points F & G are in the exterior of the angle

Example 4-1a Name all angles that have B as a vertex. Answer:  5,  6,  7, and  ABG

Example 4-1b Name the sides of  5. Answer: and or are the sides of  5.

Example 4-1c Write another name for  6. Answer:  EBD,  FBD,  DBF, and  DBE are other names for  6.

Classifying Angles An angle with measure = 90  is called a right angle

Classifying Angles An angle with measure < 90  is called an acute angle

Classifying Angles An angle with 180  > measure > 90  is called an obtuse angle

Example 4-2a Measure  TYV and classify it as right, acute, or obtuse.  TYV is marked with a right angle symbol, so measuring is not necessary. Answer: is a right angle.

Example 4-2b Measure  WYT and classify it as right, acute, or obtuse. is an obtuse angle. Answer: = > is an obtuse angle.

Example 4-2c Measure  TYU and classify it as right, acute, or obtuse. Use a protractor to find that m Answer: is an acute angle.

Lesson Summary: Objective: The students will learn how to measure angles and how to classify them according to the angle.

Preview of the Next Lesson: Objective: The students will learn the Angle Addition Postulate and about different types of angle pairs.

Homework Geometry 1-4