1. 1.4 Measuring Angles
by: Keri Adams
Focus Question: How do you
measure an angle with an angle
ruler and a protractor?

2. Investigation 1.4 Materials
• Angle rulers
• Protractors
• Labsheet 1.4 (Question E Angles)

3. Investigation 1.4 Vocabulary
• Complimentary angles
• Supplementary angles

4. Measuring Angles
Video
Launch:
http://dashweb.pearsoncmg.com/main.html

5. Can you estimate these measurements?
Prior Knowledge Connection:
http://www.wyzant.com/help/math/geometry/lines_and_angles/introduction_to_angles

6.  Which of these shapes has the smallest angle measure?
 Which has the angle with the largest measure?
 Can you find a 90⁰ angle in one of these shapes? How do you know it is 90⁰?
 How do the angles in Shape D compare to a right angle? Are their measures
greater than or less than a right angle?
 What would be a reasonable estimate of the measure of the greatest angle
of Shape D? How do you know?
Presenting the Challenge:
http://dashweb.pearsoncmg.com/main.html

7. http://etc.usf.edu/clipart/42000/42068/protractorf_42068.htm
Introduction:
What is a protractor
and how do you use it?
What is an angle ruler
and how do you use it?
http://www.schoolmart.com/angleruler.aspx

8. Your turn…
Work with your groups to complete Questions A-C.
Make sure you sketch each shape and label the
angle measures on each shape.
Explore:

9. What strategies did your group use
to estimate the measures of the
angles?
Summary:
Question A:

10. What were some of your angle
measurements?
Summary:
Question B:
http://dashweb.pearsoncmg.com/main.html

11. What angles are acute, obtuse, or right?
Summary:
Question C:
http://dashweb.pearsoncmg.com/main.html

12. Complementary Angles: Pair of angles whose
measure add to 90⁰
Supplementary Angles: Pair of angles whose
measure add to 180⁰
Pairs of complementary
angles:
Pairs of supplementary
angles:
Summary:
Question D:
http://dashweb.pearsoncmg.com/main.html

13. Summary:
Question E:
http://dashweb.pearsoncmg.com/main.html

14. How do you decide the number of
degrees for angles between the 5⁰
intervals on the angle ruler?
What things do you check to make sure
you are making accurate measurements?
Which tool do you prefer for measuring
angles? Why?
Summary:
Question E Cont.:

15. Homework:
Page 29
#19-28 (for #22-24 explain how you got your answer),
#31a & b
#32a & d
**You will need a protractor for your homework!!

16. Lesson from,
Lappan, Phillips, Fey, Friel. (2014)
Connected Mathematics 3 Shapes and
Designs. Boston: Pearson. Print.