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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 1/360th of a circle
Vocabulary
• Ray
A ray is part of a line. It has one endpoint and
extends forever in one direction.
P
Q
Naming Rays
The name of a ray shows the endpoint first and
then any other point on the ray
P
This ray is PQ (not QP!)
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
Two
A point
raysonwith
a line
a common
is the endpoint
endpoint
of that
two form
rays a
180
ondegree
that line
angle
called
areopposite
called Opposite
rays
Rays.
P
Q
R
Here the opposite rays are QP and QR
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
Name all angles that have B as a vertex.
Answer: 5, 6, 7, and ABG
Name the sides of 5.
Answer:
and
or
are the sides of 5.
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
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.
Measure WYT and classify it as
right, acute, or obtuse.
Answer:
=
is an obtuse> angle.
is an obtuse angle.
Measure TYU and classify it as
right, acute, or obtuse.
Answer: Use a protractor to find that m
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