Triangles can be sorted in different ways.  One way is by the length 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:  1)  2)  3) We’re going to find out what they are!

Let’s build triangles!  Take out the pieces from your bag. Use same-color straws to make three different kinds of triangles.  Discuss properties of the triangles with your table.

End day 1

Draw a red line around the perimeter of the equilateral triangles in this picture. All sides are the same length. Start day 2

Draw a blue line around the perimeter of the isosceles triangles in this picture. Start day 2 2 sides are the same length.

Draw a green line around the perimeter of the scalene triangles in this picture. Start day 2 No sides are the same length.

There are three ways to classify by length of sides: All sides are the same length. 2 sides are the same length. No sides are the same length.

There is another way to classify triangles… What do you think it could be?

You can also classify triangles by the measures of their angles. There are three ways!  1)  2)  3) We’re going to find out what they are!

Let’s make 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!

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!

Glue your triangles onto your poster. Label your poster.

White board activity:  Draw an isosceles obtuse triangle.

White board activity:  Draw an equilateral acute triangle.

White board activity:  Draw a scalene right triangle.

Homework: Homework 16.5