Page 123 - Math Course 2 (Book 2)

Classifying Triangles
Mo. 10

Lesson 2 Key Concept

Angles of a Triangle
KEY CONCEPTS:

1. Find the missing angle measure of a Words The sum of the measures of the angles
triangle. of a triangle is 180 o
2. Classify triangles by properties and Symbols x + y + z = 180
attributes.

Model x°

y° z°
MO. 10 - L2a
Type of Angles
Angle Measure of a Triangle Acute Angle Right Angle

Vocabulary A-Z

Let us learn some vocabulary A A
O° < m? A < 90° m? A = 90°

line segment Obtuse Angle Straight Angle
A line segment is part of a line containing two
endpoints and all of the points between them.

A B

A A
triangle 90° < m? A < 180° m? A = 180°
A triangle is formed by three line segments that
intersect only at their endpoints.
Let’s Begin
B

Find Angle Measures
A C
Example
vertex
The vertex of each angle is a vertex of the triangle.
Vertices is the plural of vertex. Find the value of x in ΔDEF.

Vertex D
A

100°
Vertex
C
Common point B Common point of 33° X°
of two rays two line segments E F

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