Lesson 9-9 Symmetry.notebook

Lesson 9­9 Symmetry.notebook
March 04, 2013
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Lesson 9­9 Symmetry.notebook
March 04, 2013
Lesson 9­9 Symmetry and Reflections
Reflectional Symmetry
When one half is a mirror image of the other half.
Line of Symmetry
A line that divides a figure with reflectional symmetry into 2 congruent halves.
Reflection
A transformation that flips a figure over a line of reflection.
Line of Reflection A line across which a figure is reflected.
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Lesson 9­9 Symmetry.notebook
March 04, 2013
A figure has line symmetry if you can draw a line through it to form two congruent shapes that are reflections of each other.
Line Symmetry
Notes
A rectangle has 2 lines of symmetry.
How many lines of symmetry do you think a circle has?
How many lines of symmetry do these figures have?
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Lesson 9­9 Symmetry.notebook
March 04, 2013
Line Symmetry can be found in everyday objects. You can't escape line symmetry!!!!! It's EVERYWHERE!
How many lines of symmetry does the United States flag have?
0 ­­ Zero!
Erase here to find out!
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Lesson 9­9 Symmetry.notebook
March 04, 2013
How many lines of symmetry can be found in each of the regular polygons below?
What can you conclude about the lines of symmetry found in regular polygons?
Pull
The number of lines of symmetry in regular polygons is equal to the number of sides.
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Lesson 9­9 Symmetry.notebook
March 04, 2013
A figure has rotational symmetry if, when rotated less than 360
a central point, it coincides with istelf.
o around Rotational Symmetry
Notes
90o
0o
180o
270o
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Lesson 9­9 Symmetry.notebook
March 04, 2013
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Lesson 9­9 Symmetry.notebook
March 04, 2013
Rotational Symmetry
90o
Pull
etermined by ated and fit on itself.
What will the X look like
after a 90 o turn?
It will look the same.
0o
180o
Turn the X to see its order of rotational symmetry.
It is Order 4
270o
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Lesson 9­9 Symmetry.notebook
March 04, 2013
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