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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 inversion (C i). "Equal" is meant here as the same up to conjugacy ...
These six planes of projection intersect each other, forming a box around the object, the most uniform construction of which is a cube; traditionally, these six views are presented together by first projecting the 3D object onto the 2D faces of a cube, and then "unfolding" the faces of the cube such that all of them are contained within the ...
In geometry, many uniform tilings on sphere, euclidean plane, and hyperbolic plane can be made by Wythoff construction within a fundamental triangle, (p q r), defined by internal angles as π/p, π/q, and π/r. Special cases are right triangles (p q 2).
Note that with the cube (see image) the perimeter of the resulting 2D drawing is a perfect regular hexagon: all the black lines have equal length and all the cube's faces are the same area. Isometric graph paper can be placed under a normal piece of drawing paper to help achieve the effect without calculation.
A cross-section of a solid right circular cylinder extending between two bases is a disk if the cross-section is parallel to the cylinder's base, or an elliptic region (see diagram at right) if it is neither parallel nor perpendicular to the base. If the cutting plane is perpendicular to the base it consists of a rectangle (not shown) unless it ...
Uniform tilings can exist in both the Euclidean plane and hyperbolic plane. Uniform tilings are related to the finite uniform polyhedra; these can be considered uniform tilings of the sphere. Most uniform tilings can be made from a Wythoff construction starting with a symmetry group and a singular generator point inside of the fundamental ...
Further associated with each plane is a unique line, called the plane's pole, that passes through the origin and is perpendicular to the plane. This line can be plotted as a point on the disk just as any line through the origin can. So the stereographic projection also lets us visualize planes as points in the disk.
The difference between the prismatic and antiprismatic symmetry groups is that D ph has the vertices lined up in both planes, which gives it a reflection plane perpendicular to its p-fold axis (parallel to the {p/q} polygon); while D pd has the vertices twisted relative to the other plane, which gives it a rotatory reflection.