Triangles can be sorted in Triangles can be sorted in different ways.different ways.

One way is by the One way is by the length of their sideslength of their sides. .

Examine, or look closely, at the triangles in

this picture.

What do you notice about the length of

the sides of the triangles?

There are three ways:There are three ways:

1)1)

2)2)

3)3)

We’re going to

find out what

they are!

Let’s build triangles! Let’s build triangles!

Take out the pieces from your bag. Use Take out the pieces from your bag. Use same-color straws to make three different same-color straws to make three different kinds of triangles.kinds of triangles.

Discuss properties of the triangles with Discuss properties of the triangles with your table. your table.

End day 1

Draw aDraw a red linered line around around

the the perimeter perimeter

of the of the equilateraequilateral trianglesl triangles

in this in this picture.picture.

All sides are

the same length.

Start day 2

Draw aDraw a blue lineblue line around around

the the perimeter perimeter

of the of the isosceles isosceles trianglestriangles

in this in this picture.picture.

Start day 2

2 sides are the same

length.

Draw aDraw a green linegreen line

around around the the

perimeter perimeter of the of the

scalene scalene trianglestriangles

in this in this picture.picture.

Start day 2

No sides are the same

length.

There are three ways to There are three ways to classify by classify by length of length of sidessides::

All sides are

the same length.

2 sides are the same

length.

No sides are the same

length.

There is another way to There is another way to classify triangles…classify triangles…

What do you What do you think it could think it could

be?be?

You can also classify triangles by You can also classify triangles by the the measures of their angles.measures of their angles.

There are three ways!There are three ways! 1)1)

2)2)

3)3)

We’re going to

find out what

they are!

Let’s make Let’s make triangles! triangles!

Triangle #1-

• Fold your square paper diagonally in half.

• Unfold. Cut on the fold to make two triangles.

• Mark the 90 degree angle with a square in the corner.

• Label triangle.

Triangle #2-

• Choose one of the two remaining pieces of paper.

• Draw an obtuse angle.

• Draw a third line to make a triangle.

• Cut out your triangle.

• Label triangle.

Let’s make triangles!Let’s make triangles!

Triangle #3-

• On the last piece of paper, draw a triangle with ALL acute angles.

• Cut out your triangle.

• Label triangle.

Let’s make triangles!Let’s make triangles!

Glue your triangles onto Glue your triangles onto your poster. Label your your poster. Label your poster.poster.

White board activity: White board activity:

Draw an isosceles obtuse triangle. Draw an isosceles obtuse triangle.

White board activity: White board activity:

Draw an equilateral acute triangle. Draw an equilateral acute triangle.

White board activity: White board activity:

Draw a scalene right triangle. Draw a scalene right triangle.

Homework: Homework Homework: Homework 16.516.5