1. A right triangle is a triangle with a right angle
So far in this chapter, you have found the areas of different shapes by dividing them into smaller pieces and then putting the pieces back together to make rectangles.  In this lesson, you will look at strategies for making shapes larger to find their areas.  As you work today, consider these questions with your team:
How can we make a rectangle or parallelogram?
How are the areas related ?
Which lengths help us find the area?
An acute triangle is a triangle with all three angles acute (less than 90°).
An obtuse triangle is one with one obtuse angle (greater than 90°) and two acute angles.
A right triangle is a triangle with a right angle

2. 85. AREA CHALLENGE — TRIANGLES
Think about how you might find the area of the obtuse triangle shown at right.
Can you cut and rearrange the obtuse shape to make a rectangle?
What if you had two copies of this obtuse triangle?  What shapes could you make by putting the copies together? 
Get a set of triangles from the Lesson 5.3.3A Resource Page.
Carefully cut out the obtuse triangle by cutting along the sides of the figure.
Find the person in your team who has a triangle that matches yours in size and shape.  This person will be your partner for this activity.
Work with your partner to combine the two triangles into a four-sided shape.  Sketch the shapes that you create on your paper. . 
c) What about the triangles that are not obtuse?  Cut out the other two triangles from the resource page.  Work with your partner to combine the two acute triangles.  Sketch your results.  Can any of your arrangements be formed into a  rectangle?
d) Repeat the process you used in part (c) for the two right triangles.

3. 86. Look carefully at the shapes you created in problem #85 that can be cut and rearranged into rectangles.
Label the shapes in #85.  What are they called?
What lengths would you need to know to find the area of each rectangle?  Where can you find those lengths on the parallelograms before you rearrange them into rectangles?  Draw and label them on your circled sketches. 
How is the area of each parallelogram that you circled related to the area of the two triangles that made it? 
Darla created the shape at right out of two triangles and has measured and labeled some of the lengths.  Which measurements should she use to find the area of the shaded triangle?  What is the area of the shaded  triangle?
Where else could you draw the height on Darla’s shape?

4. 87. Leticia is looking at a triangle (see her figure below)
87. Leticia is looking at a triangle (see her figure below).  “I know how it can be copied and made into a parallelogram, which can then be made into a rectangle,” she said, “But when I look at this shaded triangle, I see it inside a rectangle  instead.”
What fraction of the rectangle is this triangle?  Work with your team to justify your ideas.  Be sure to include a labeled diagram as part of your explanation.
88. Describe how to find the area of any triangle.  That is, when a triangle has a base of length  b  and a height of length  h, what expression can be used to calculate the area of the triangle?

5. 90. LEARNING LOG
Label this entry, “Areas of Parallelograms and Triangles” and include today’s date.
Describe how to find the areas of parallelograms and triangles.  This entry does not ask you simply to write a formula.  Instead, for each description:
Sketch an example shape and show how you can find the area.
Explain how finding the area of each type of shape is similar and how it is different. 

6. Tonight’s homework is… 5.3.3 Review & Preview, problems # 91-95
Show all work and justify your answers for full credit.
Review “Methods and Meanings” Area of Parallelogram vimeo