Lines of Symmetry
Lines of Symmetry
A figure has line symmetry, or
reflectional symmetry, if there is a
reflection for which the figure is its
own image.
Examples
of
lines of
symmetry
NON
-examples
of lines of
symmetry
Rotational Symmetry
If you can
rotate
(or turn) a figure around a center point by fewer
than 360° and the figure appears unchanged, then the figure has
rotational symmetry
.
The point around which you rotate is called the
center of rotation
.
The smallest angle you need to turn is called the
angle of rotation
.
Rotational Symmetry Examples
This figure has
rotational symmetry
of 72°, and the center of
rotation is the center of the figure:
Other examples of rotational symmetry:
Hmmmm…
How can you find the # of
lines of symmetries
for any
regular polygon?
How do you find the
angle of rotation
of any regular
polygon?
Reflectional Symmetry
The number of lines of symmetry is equal to the
number of sides.
Rotational Symmetry
Ex:
What regular polygons have 90°
rotational symmetry? Explain
your reasoning.
.
squares
A comprehensive guide to lines of symmetry and rotational symmetry in figures, including examples and explanations for regular polygons. Discover how to determine the number of lines of symmetry and the angle of rotation for different shapes.
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Presentation Transcript
Lines of Symmetry A figure has line symmetry, or reflectional symmetry, if there is a reflection for which the figure is its own image.
Examples of lines of symmetry NON-examples of lines of symmetry
Rotational Symmetry If you can rotate (or turn) a figure around a center point by fewer than 360 and the figure appears unchanged, then the figure has rotational symmetry. The point around which you rotate is called the center of rotation. The smallest angle you need to turn is called the angle of rotation.
Rotational Symmetry Examples This figure has rotational symmetry of 72 , and the center of rotation is the center of the figure: Other examples of rotational symmetry:
Hmmmm How can you find the # of lines of symmetries for any regular polygon? How do you find the angle of rotation of any regular polygon?
Reflectional Symmetry The number of lines of symmetry is equal to the number of sides.
Rotational Symmetry Angle of rotation for regular polygons is: 360 ? where n is the number of sides. Ex: 360 5= 72 360 6= 60
What regular polygons have 90 rotational symmetry? Explain your reasoning. . squares
