symétrie de révolution d'ordre n

OBS: Proposition de M. Jean-Marc TERRIER, professeur de mathématiques à l'Université de Montréal, après qu'il ait consulté un collègue cristallographe.

CONT: ""symmetry"": In general, a figure or expression is said to be symmetric if parts of it may be interchanged without changing the whole. ... A right circular cone has an axis of symmetry. A geometric figure has n-fold rotational symmetry about an axis if a rotation of 360°/n is a symmetry of the figure. Thus an axis of symmetry can be a rotational axis. For example, an axis through the centre of a square perpendicular to the plane is a 4-fold axis since a rotation of 360°/4 produces an identical figure; a diagonal is a 2-fold axis.