but don't remove them.

Transcription

1 The following pages have been created by Robert Dawson All pages with a brown background are notes for the teacher. Just skip them during the lesson, but don't remove them. May 2006 I give permission for K12 teachers only to use this copyrighted lesson in a classroom only if you agree to the following: 1) None of the brown pages are deleted. 2) You make no money from using the lesson. Otherwise, I hope it helps and have fun teaching. - Robert Dawson Teacher's Notes Subject: Mathematics Topic: How To Use A Protractor Grade Level: Middle School Title: teacher notes (1 of 40)

2 How To Use A Protractor Two Major Ideas 1) How to correctly place the protractor 2) How to correctly read the protractor protractor - A tool to measure angles. Title: major ideas (2 of 40)

3 Title: real pro wo labels (3 of 40)

4 Outer Scale Inner Scale Zero-Edge Center Mark Title: real pro w labels (4 of 40)

5 Title: state pro wo labels (5 of 40)

6 Outer Scale Inner Scale Zero-Edge Center Mark Title: state pro w labels (6 of 40)

7 Vocabulary Words zero-edge center mark inner scale outer scale Title: vocabulary words (7 of 40)

8 Vocabulary Words zero-edge center mark inner scale outer scale Title: vocabulary words (8 of 40)

9 Vocabulary Words zero-edge center mark inner scale outer scale Title: vocabulary words (9 of 40)

10 Vocabulary Words zero-edge center mark inner scale outer scale Title: vocabulary words (10 of 40)

11 Vocabulary Words zero-edge center mark inner scale outer scale Title: vocabulary words (11 of 40)

12 Teacher's Notes The next page is a guide for answers from the previous page. Title: teacher notes (12 of 40)

13 Vocabulary Words zero-edge center mark The zero-edge is always at the same level as the 0 degree mark. The center mark is always at the middle of the zero-edge. inner scale The numbers on the inner edge of the protractor. outer scale The numbers on the outer edge of the protractor. Title: vocabulary words (13 of 40)

14 Measuring an Angle Step 1) Determine if the angle is acute or obtuse before using the protractor. Title: measure step 1 (14 of 40)

15 Measuring an Angle Step 2) Place the center mark of the protractor on the vertex of the angle Title: measure step 2 (15 of 40)

16 Measuring an Angle Step 3) Rotate the zero-edge of the protractor to line up with one ray of the angle and for the other ray of the angle to cross the protractor's scale. Title: measure step 3 (16 of 40)

17 Measuring an Angle Step 4) Read the measure of the angle of the ray that crosses the protractor's scale. Title: measure step 4 (17 of 40)

18 Title: enlarged step 4 (18 of 40)

19 Practice with the Protractor Used on the State Test Title: measure w state pro (19 of 40)

20 Step 1) Measuring an Angle Step 2) Step 3) Step 4) Title: angle directions (20 of 40)

21 Step 1) Measuring an Angle Step 2) Step 3) Step 4) Title: angle directions (21 of 40)

22 Step 1) Measuring an Angle Step 2) Step 3) Step 4) Title: angle directions (22 of 40)

23 Step 1) Measuring an Angle Step 2) Step 3) Step 4) Title: angle directions (23 of 40)

24 Step 1) Measuring an Angle Step 2) Step 3) Step 4) Title: angle directions (24 of 40)

25 Teacher's Notes The next page is a guide for answers from the previous page. The directions on the next were adapted by Robert Dawson, but the directions are from the following source: Discovering Geometry: An Investigative Approach, Key Curriculum Press, th Street, Emeryville, CA 94608, MATH, Title: teacher notes (25 of 40)

26 Step 1) Determine if the angle is acute or obtuse before using the protractor. This will help you later when you need to decide which scale to use, the inner scale or the outer scale. Measuring an Angle Step 2) Place the center mark of the protractor on the vertex of the angle. Step 3) Rotate the zero-edge of the protractor to line up with one side of the angle and for the other side of the angle to cross the protractor's scale. Step 4) Read the measure of the angle of the side that crosses the protractor's scale. If the angle is acute, the use the scale where the numbers surrounding the line crosses the scale are less than 90. If the angle is obtuse, the use the scale where the numbers surrounding the line crosses the scale are greater than 90. Title: angle directions (26 of 40)

27 Common Mistakes 1) Using the incorrect scale. 2) The center mark is not on the vertex. This usually happens after rotating the protractor. Make sure after rotating the protractor that the cente mark is still on the vertex. 3) Counting the marks in the wrong direction. Pay attention to whether the numbers are increas or decreasing. Title: common mistakes (27 of 40)

28 Teacher's Notes The next four pages focus on using the correct scale. The next two pages after the above pages focus on counting the marks in the correct direction. Title: teacher notes (28 of 40)

29 Is the measure of the angle 130 or 50 degrees? Explain. Title: reading correctly 1 (29 of 40)

30 Is the measure of the angle 20 or 160 degrees? Explain. Title: reading correctly 2 (30 of 40)

31 Is the measure of the angle 70 or 110 degrees? Explain. Title: reading correctly 3 (31 of 40)

32 Is the measure of the angle 80 or 100 degrees? Explain. Title: reading correctly 4 (32 of 40)

33 Is the measure of the angle 53 or 47 degrees? Explain. Title: reading correctly 5 (33 of 40)

34 Is the measure of the angle 106 or 114 degrees? Explain. Title: reading correctly 6 (34 of 40)

35 Teacher's Notes The next four pages are angles in different positions. Discuss with students how you would turn the protractor or page. Each angle is grouped with the picture of the page so that the page can be rotated with the angle except for the page where the two rays are too short. The page and the original angle are locked in place. Title: teacher notes (35 of 40)

36 Title: rays up (36 of 40)

37 Title: ray down (37 of 40)

38 Teacher's Notes The next class page is an example of an angle where the rays are too short. Trying to extend the rays during a lesson using the straight line tool can be tedious. So I solved the problem by doing the following: 1) There is a copy of the two rays on top of the original angle that are not grouped and not locked in place. 2) The original angle and paper are locked in place. 3)Just tap on one of the rays during the lesson and drag it to extend it. Do the same for the other ray. Title: teacher notes (38 of 40)

39 Title: rays short (39 of 40)

40 Title: ray left side (40 of 40)