Rotational Symmetry

Transcription

Rotational Symmetry
Multi-Part Lesson
9-3
Symmetry
PART
Main Idea
I will identify and
describe reflections.
New Vocabulary
rotational symmetry
macmillanmh.com
A
B
C
Rotational Symmetry
You have learned that images can reflect over a line of
symmetry to show line symmetry. Images that lie in the
same position after rotating 180° or less around a point
have rotational symmetry .
A snowflake shows rotational symmetry.
Materials
construction or plain
paper
scissors
Mini-Activity
Create a design that shows rotational symmetry.
Step 1
EXP-Scissors
Fold paper.
Fold a square piece of paper into
8 equal pieces as shown.
Step 2 C09-278A-112056
Cut paper.
C09-281A-112056
C09-280A-112056
C09-279A-112056
Keep the paper folded. Cut shapes out of the sides.
Step 3
Unfold paper.
C09-282A-112056
Unfold the paper to see the design that shows
rotational symmetry.
C09-283A-112056
454
Chapter 9 Angles and Transformations
454_457_C09_L03_112056.indd 454
7/14/09 11:32:21 AM
Identify Rotational Symmetry
Tell whether each figure shows rotational symmetry.
Write yes or no.
The starfish will lie in the same position after rotating 180°
or less around its center.
So, the starfish has rotational symmetry.
The dragonfly does not rotate around a point.
So, the dragonfly does not have rotational symmetry.
Tell whether each figure shows rotational symmetry. Write yes
or no. See Examples 1 and 2 (p. 455)
1.
2.
4. Kelvin has a bicycle. Does each
C09-284A-112056
tire show rotational symmetry?
Explain.
5.
3.
C09-430A-112056
Describe a real-world example of
rotational symmetry.
Lesson 9-3 Symmetry 455
454_457_C09_L03_112056.indd 455
7/14/09 11:32:27 AM
EXTRA
%
)# E
# T4 IC
!C
2A
0R
P
See page R29.
Tell whether each figure shows rotational symmetry. Write yes
or no. See Examples 1 and 2 (p. 455)
6.
7.
8.
9.
10.
11.
C09-286A-112056
C09-287A-112056
C09-288A-112056
12. Does the leaf below show rotational
13. Does the wagon wheel
below show
C09-289A-112056
symmetry? Explain.
rotational symmetry? Explain.
14. Does the movement of the gymnast
15. Do all real-world objects that are in the
around the bar show a rotation? Explain.
shape of a circle show rotational
symmetry? Explain.
16. OPEN ENDED Draw a shape that has rotational symmetry.
17. WHICH ONE DOESN’T BELONG? Which shape does not belong
with the other three? Explain.
18.
456
Is it possible for a shape to have both line
and rotational symmetry? Explain.
C09-290A-112056 C09-291A-112056C09-292A-112056C09-293A-112056
Chapter 9 Angles and Transformations
454_457_C09_L03_112056.indd 456
7/27/09 11:16:28 AM
Practice
19. Rotational symmetry can be seen in
many flowers. Which flower does
NOT show rotational symmetry?
20. Terry wrote four names. Which
name shows line symmetry?
F. TIM
A.
G. KIM
H. JAN
I. BOB
B.
C.
21. Some pattern blocks show
rotational symmetry. Which pattern
block does NOT show rotational
symmetry?
A. triangle
B. trapezoid
D.
C. square
D. hexagon
Tell whether each figure has line symmetry. Write yes or no.
If yes, tell how many lines of symmetry the figure has. (Lesson 9-3B)
22.
23.
24. C09-298A-112056
C09-299A-112056
25.
C09-301A-112056
C09-300A-112056
26. Chung is having a snack. What transformation does the apple
represent? Explain. (Lesson 9-2E) reflection; The line of reflection
Lesson 9-3 Symmetry 457
454_457_C09_L03_112056.indd 457
7/14/09 11:32:39 AM

Similar documents