Interior Angles of a Triangle

PHASE 1

To begin, you must first review the following geometric vocabulary and concepts: Triangle, Angle, Straight Angle, Line Segment, Interior Angle, Exterior Angle, Adjacent angle

You will also recall, the types of triangles based on sides and angles. Watch the following video (0:00 - 6:15) to aid your review.

PHASE 2

Now we are ready to begin.

You will perform a series of activities during and or after which you are expected to answer the following questions. This should be done in word document and submitted at the end of the activity. The questions are:

1. How is the Triangle Angle Sum Theorem based on the measure of a straight angle?
2. How can we find missing angle measures in triangles and how can this knowledge be used to solve real world problems?
3. Where do we see examples of the Triangle Angle Sum Theorem outside of the classroom? See Guiding Question 3. word document for examples and applicable websites.

First, you will discover the Triangle Interior Angle Theorem using paper models.

1. Using pencil, construction paper or blank sheet, rulers and scissors, you will draw and cut out triangles of various types and sizes. Label the interior angles of each triangle A, B and C before cutting them out.

Consider this:
Do they think the sum of the angles will always be the same? Or will it be greater for larger triangles?

2. On another blank sheet, use your rulers to draw a straight line.

3. Cut out angles A, B and C.

4. Take the cut outs of angle A and C and place them adjacent to each other on the straight line.

5. Now place Angle B adjacent to angle C on the straight line.

What do you notice?

Key observation: The triangle's 3 interior angles add up to 180 degrees (or form a straight angle or straight line).

6. Then, you will continue to investigate and discover angle measurements by exploring the Investigating the Triangle Angle Sum Theorem dynamic worksheet via computer and internet connection.

7. During the computer-based activity, you will record your findings on the  Investigating the Triangle Angle Sum Theorem PDF worksheet.  

PHASE 3

8. Upon completion of the computer-based activity, working independently or in small groups, you will complete the "Finding Interior Angles of Triangles Guided Practice" worksheet. See attachment below.

(Solutions are provided - see attachment below). Check your level of mastery. 

9. To conclude, you will complete practice problems involving numeric and algebraic values.

See worksheet: Finding Interior Angles of Triangles.docx.

Submit All Completed Work to the following Email: [email protected]