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Rotational symmetry of order n, also called n-fold rotational symmetry, or discrete rotational symmetry of the n th order, with respect to a particular point (in 2D) or axis (in 3D) means that rotation by an angle of (180°, 120°, 90°, 72°, 60°, 51 3 ⁄ 7 °, etc.) does not change the object.
A hierarchy of 4D point groups and some subgroups. Vertical positioning is grouped by order. Blue, green, and pink colors show reflectional, hybrid, and rotational groups.
The conjugate of that eigenvalue is also unity, yielding a pair of eigenvectors which define a fixed plane, and so the rotation is simple. In quaternion notation, a proper (i.e., non-inverting) rotation in SO(4) is a proper simple rotation if and only if the real parts of the unit quaternions Q L and Q R are equal in magnitude and have the same ...
The tetrahedral group of order 12, rotational symmetry group of the regular tetrahedron. It is isomorphic to A 4. The conjugacy classes of T are: identity; 4 × rotation by 120°, order 3, cw; 4 × rotation by 120°, order 3, ccw; 3 × rotation by 180°, order 2; The octahedral group of order 24, rotational symmetry group of the cube and the ...
The theorem also excludes S 8, S 12, D 4d, and D 6d (see point groups in three dimensions), even though they have 4- and 6-fold rotational symmetry only. Rotational symmetry of any order about an axis is compatible with translational symmetry along that axis. The result in the table above implies that for every discrete isometry group in four ...
In the 5 cases of rotational symmetry of order 3 or 6, the unit cell consists of two equilateral triangles (hexagonal lattice, itself p6m). They form a rhombus with angles 60° and 120°. In the 3 cases of rotational symmetry of order 4, the cell is a square (square lattice, itself p4m).
D 1 and C 2: group of order 2 with a single 180° rotation; D 1h and C 2v: group of order 4 with a reflection in a plane and a 180° rotation through a line in that plane; D 1d and C 2h: group of order 4 with a reflection in a plane and a 180° rotation through a line perpendicular to that plane. S 2 is the group of order 2 with a single ...
D 3, D 4 etc. are the symmetry groups of the regular polygons. Within each of these symmetry types, there are two degrees of freedom for the center of rotation, and in the case of the dihedral groups, one more for the positions of the mirrors. The remaining isometry groups in two dimensions with a fixed point are: