| 释义 |
rotational symmetry A plane figure has rotational symmetry about a point O if rotation about O through some angle 0∘<θ<360∘ is a symmetry of the figure. For example, an equilateral triangle has rotational symmetry about its centre. The order of rotational symmetry about O is the number of such rotations in the range 0∘≤θ<360∘; so, the equilateral triangle has order 3.
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