Operation of Rotation through 90 Degree and 180 Degree of Simple Figures
The recycling icon is a very common symbol, and like most effective icons, the image itself is suggestive of its meaning. The arrows of the image appear to be moving in a circular manner, suggesting the circular concept of recycling.
Adding to this perception is that if you were to rotate the image 120 degrees, and another 120 degrees, and a third 120 degrees, it would look the same at all three stops.
Other shapes which have rotational symmetry are rectangles, squares, circles, and all regular polygons.
You may choose an object of any particular shape and rotate it up to 180 degrees around its center. If at any point the object appears exactly like it did before the rotation, then the object has rotational symmetry.