Lesson 62: Classifying Triangles

Lesson 62: Classifying Triangles

How do I identify a triangle by its sides?

How do I identify a triangle by its angles?

Open up to

page 59 in

your

notebooks!

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Multiple Choice

What type of angle is this?

• acute

• right

• obtuse

Multiple Choice

What type of angle is this?

• acute

• right

• obtuse

Multiple Choice

What type of angle is this?

• acute

• right

• obtuse

Did you remember them all?!

Key Idea #1

We can name triangles based on their angles:

• All the angles of ACUTE triangles are less than 90 degrees.

• A RIGHT triangle had one angle that is 90 degrees.

• An OBTUSE triangle has one angle greater than 90 degrees.

Multiple Choice

A triangle where all of the angles are less than 90 degrees is called a(n)

• equilateral triangle

• acute triangle

• obtuse triangle

• right triangle

Multiple Choice

A triangle where one angle is greater than 90 degrees is called a(n)

• equilateral triangle

• obtuse triangle

• isosceles triangle

• scalene triangle

Key Idea #2

Each angle of a triangle has a side that is OPPOSITE that angle.

Key Idea #3

The LONGEST side of a triangle is OPPOSITE the LARGEST angle.

Which side is the longest?

​Side AC

Key Idea #4

The SHORTEST side of a triangle is OPPOSITE the SMALLEST angle.

​Side AB

Key Idea #5

If two angles in a triangle have the SAME MEASURE, then the side opposite those angles have the SAME LENGTH. Which two sides have the same length?

​Side AB, AC

Key Idea #6

A regular triangle is called an EQUILATERAL triangle.

What makes it a regular triangle?

It has sides that are all the same length and angles all the same measure

Key Idea #7

Triangles can be identified by their sides.

• Equilateral Triangle: all sides are the same length.

• Isosceles Triangles: two sides are the same length

• Scalene Triangle: no sides are the same length.

Multiple Choice

A triangle where all three sides are the same length is called

• equilateral triangle

• obtuse triangle

• isosceles triangle

• scalene triangle

Multiple Choice

A triangle where all two sides are the same length is called

• equilateral triangle

• obtuse triangle

• isosceles triangle

• scalene triangle

Multiple Choice

A triangle where all three sides are of UNEQUAL length is called

• equilateral triangle

• obtuse triangle

• isosceles triangle

• scalene triangle

Complete the "practice set" before beginning your homework.

Show Mrs. Krieger