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(2) Rotation The "rotation" of two-dimensional shapes can be used in the following two ways. One is the rotation on the same two-dimensional plane, and the other is the rotation of a solid shape drawn in the three dimensional space. In the latter case, the rotation of 180 degrees is equivalent with the operation of the "mirror reflection". An arrangement of petals mostly shares both operations of the "rotation" and "mirror reflection". Three examples using the former operation of the
rotation in the same plane are shown here. Shapes which coincide by 90
or 180 degree rotation are shown here. But there are some cases when a
small angle rotation is useful such as moiré patterns of printing.
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