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  2. Central line (geometry) - Wikipedia

    en.wikipedia.org/wiki/Central_line_(geometry)

    The special property that distinguishes a straight line as a central line is manifested via the equation of the line in trilinear coordinates. This special property is related to the concept of triangle center also. The concept of a central line was introduced by Clark Kimberling in a paper published in 1994. [1] [2]

  3. Fixed points of isometry groups in Euclidean space - Wikipedia

    en.wikipedia.org/wiki/Fixed_points_of_isometry...

    In the case of a physical body, if for the symmetry not only the shape but also the density is taken into account, it applies to the centre of mass. If the set of fixed points of the symmetry group of an object is a singleton then the object has a specific centre of symmetry. The centroid and centre of mass, if defined, are this point.

  4. Point groups in three dimensions - Wikipedia

    en.wikipedia.org/wiki/Point_groups_in_three...

    All symmetry groups in the 7 infinite series are different, except for the following four pairs of mutually equal ones: C 1h and C 1v: group of order 2 with a single reflection (C s) 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 ...

  5. Point reflection - Wikipedia

    en.wikipedia.org/wiki/Point_reflection

    An object that is invariant under a point reflection is said to possess point symmetry (also called inversion symmetry or central symmetry). A point group including a point reflection among its symmetries is called centrosymmetric. Inversion symmetry is found in many crystal structures and molecules, and has a major effect upon their physical ...

  6. List of character tables for chemically important 3D point groups

    en.wikipedia.org/wiki/List_of_character_tables...

    This lists the character tables for the more common molecular point groups used in the study of molecular symmetry. These tables are based on the group-theoretical treatment of the symmetry operations present in common molecules, and are useful in molecular spectroscopy and quantum chemistry. Information regarding the use of the tables, as well ...

  7. Introduction to systolic geometry - Wikipedia

    en.wikipedia.org/wiki/Introduction_to_systolic...

    Recall the notion of central symmetry: a Euclidean polyhedron is called centrally symmetric if it is invariant under the antipodal map. Thus, in the plane central symmetry is the rotation by 180 degrees. For example, an ellipse is centrally symmetric, as is any ellipsoid in 3-space.

  8. List of planar symmetry groups - Wikipedia

    en.wikipedia.org/wiki/List_of_planar_symmetry_groups

    This article summarizes the classes of discrete symmetry groups of the Euclidean plane. The symmetry groups are named here by three naming schemes: International notation, orbifold notation, and Coxeter notation. There are three kinds of symmetry groups of the plane: 2 families of rosette groups – 2D point groups; 7 frieze groups – 2D line ...

  9. Symmetry (geometry) - Wikipedia

    en.wikipedia.org/wiki/Symmetry_(geometry)

    A drawing of a butterfly with bilateral symmetry, with left and right sides as mirror images of each other.. In geometry, an object has symmetry if there is an operation or transformation (such as translation, scaling, rotation or reflection) that maps the figure/object onto itself (i.e., the object has an invariance under the transform). [1]