Learning Objective

Students will identify attributes of triangles.

skill concept context

Prior Knowledge

On your whiteboard, draw the shape of this sign.

This shape is a triangle. Triangles come in different shapes. Today you are going to learn some new names for triangles.

triangle

Prior Knowledge

Whiteboard:Draw two differentthree-sided figures.

Share Out:Hold up your whiteboard.Look around the room to see what your classmates

have drawn.

triangle

Examples of Triangles

Triangle means “three sides”

Any three-sided shape is a trianglebut only if each of the three sides are

straight.

Non-Examples of Triangles

These are not triangles because they do not have three sides.

Why is it important to know about different triangles?

Triangles are used in buildings and bridges.

Concept Development Definition

All triangles have special names

based on the length of their sides.

Special Triangles have special names

Let’s learn about what makes these triangles special…

isosceles

equilateral

scalene

Equilateral Triangle

All triangles have special names based on the length of their sides.

A triangle thathas three sides of equal length.

4 cm4 cm

4 cm

6 cm6 cm

6 cm

Isosceles Triangle

All triangles have special names based on the length of their sides.

A triangle thathas two sides of equal length.

7 cm

4 cm

7 cm

9 cm

9 cm

5 cm

Scalene Triangle

All triangles have special names based on the length of their sides.

A triangle thathas no sides of equal length.

3 cm

5 cm

8 cm

6 cm

9 cm

4 cm

Concept Development Definition

All triangles have special names based on the length of their sides.

Guided Practice #1

Pair share: Why does the triangle have this special name?

Whiteboard: What is the special name for this triangle?

has three sides of equal length.

All triangles have special names based on the length of their sides.

6 cm6 cm

6 cmAn equilateral triangle

Guided Practice #2

Pair share: Why does the triangle have this special name?

Whiteboard: What is the special name for this triangle?

has two sides of equal length.

All triangles have special names based on the length of their sides.

7 cm

4 cm

7 cm

An isosceles triangle

Guided Practice #3

Pair share: Why does the triangle have this special name?

Whiteboard: What is the special name for this triangle?

A scalene triangle has no sides of equal length.

All triangles have special names based on the length of their sides.

3 cm

5 cm

8 cm

What is our Definition?

All triangles have special names based on the length of their sides.

Time for

Independent Practice

What Did We Learn

Students will identify triangles by their attributes.

1. Are all triangles the same?2. What is the name of a triangle with 3

sides that are the same length?3. What is the name of the triangle with 2

sides that are the same length?4. What is the name of a triangle with no

sides that are the same length?