12.2. Rotation Symmetry http://www.ck12.org
12.2 Rotation Symmetry
Here you’ll learn how to determine whether or not a shape has rotation symmetry.
What if you were asked to consider the presence of symmetry in nature? The starfish, below, is one example of
symmetry in nature. Draw in the center of symmetry and the angle of rotation for this starfish. After completing this
Concept, you’ll be able to answer questions like these.
Watch This
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter12RotationSymmetryA
MEDIA
Click image to the left for more content.Brightstorm:Rotational Symmetry
Guidance
Rotational Symmetryis when a figure can be rotated (less that 360◦) and it looks the same way it did before the
rotation. Thecenter of rotationis the point at which the figure is rotated around such that the rotational symmetry
holds. Typically, the center of rotation is the center of the figure. Along with rotational symmetry and a center of
rotation, figures will have anangle of rotation, that tells us how many degrees we can rotate a figure so that it still
looks the same. In general, if a shape can be rotated n times, the angle of rotation is^360
◦
n. Then, multiply the angle
of rotation by 1, 2, 3... , andnto find the additional angles of rotation.
Example A
Determine if the figure below has rotational symmetry. Find the angle and how many times it can be rotated.
The pentagon can be rotated 4 times and show rotational symmetry. Because there are 5 lines of rotational symmetry,
the angle would be^360
◦
5 =^72
◦. Note that the 5th rotation would be 360◦and so does not count for demonstratingrotational symmetry.