Definition of Order of Rotational Symmetry:
The number of times a figure fits into itself in one complete rotation is called the order of rotational symmetry.
If A° is the smallest angle by which a figure is rotated so that rotated from fits onto the original form, then the order of rotational symmetry is given by 360°/A° [A° < 180°]
Examples of Order of Rotational Symmetry:
We observe that while rotating the figure through 360°, it attains original from two times i.e., it looks exactly the same at two positions. Thus, we say that the rectangle has a rotational symmetry of order 2.
Equilateral triangle (clockwise):
We observe that at all 3 positions, the triangle looks exactly the same when rotated about its center by 120°.
Letter B (clockwise):
We observe that only at one position the letter looks exactly the same after taking one complete rotation.
We observe that if we rotate it by one – quarter, at 4 positions, it looks exactly the same. Therefore, the order of rotational symmetry is 4.
● Related Concepts