Geometry · Transformations
Rotational Symmetry
HSG-CO.A.3
Definition
A figure has it when a rotation of less than a full turn maps the figure onto itself.
Examples
- A regular pentagon has rotational symmetry — a 72 degree turn maps it onto itself.
- A square has rotational symmetry at 90, 180, and 270 degrees.
Key rule
The rotation must be less than 360 degrees and still map the figure onto itself.
Memory hook
Turns before a full circle, but still looks the same.