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V(3.4. 3 / 2 .4) π − π / 2 90° Hexahemioctacron (Dual of cubohemioctahedron) — V(4.6. 4 / 3 .6) π − π / 3 120° Octahemioctacron (Dual of octahemioctahedron) — V(3.6. 3 / 2 .6) π − π / 3 120° Small dodecahemidodecacron (Dual of small dodecahemidodecacron) — V(5.10. 5 / 4 ...
An antiparallelogram is a special case of a crossed quadrilateral, with two pairs of equal-length edges. [3] In general, crossed quadrilaterals can have unequal edges. [ 3 ] Special forms of the antiparallelogram are the crossed rectangles and crossed squares, obtained by replacing two opposite sides of a rectangle or square by the two diagonals.
Colored regions are cross-sections of the solid cone. Their boundaries (in black) are the named plane sections. A cross section of a polyhedron is a polygon. The conic sections – circles, ellipses, parabolas, and hyperbolas – are plane sections of a cone with the cutting planes at various different angles, as seen in the diagram at left.
A central cross section of a regular tetrahedron is a square. The two skew perpendicular opposite edges of a regular tetrahedron define a set of parallel planes. When one of these planes intersects the tetrahedron the resulting cross section is a rectangle. [11] When the intersecting plane is near one of the edges the rectangle is long and skinny.
This fact can be used to calculate the dihedral angles themselves for a regular or edge-symmetric ideal polyhedron (in which all these angles are equal), by counting how many edges meet at each vertex: an ideal regular tetrahedron, cube or dodecahedron, with three edges per vertex, has dihedral angles = / = (), an ideal regular octahedron or ...
Let φ be the golden ratio.The 12 points given by (0, ±1, ±φ) and cyclic permutations of these coordinates are the vertices of a regular icosahedron.Its dual regular dodecahedron, whose edges intersect those of the icosahedron at right angles, has as vertices the 8 points (±1, ±1, ±1) together with the 12 points (0, ±φ, ± 1 / φ ) and cyclic permutations of these coordinates.
Each polyhedron lies in Euclidean 4-dimensional space as a parallel cross section through the 600-cell (a hyperplane). In the curved 3-dimensional space of the 600-cell's boundary surface envelope, the polyhedron surrounds the vertex V the way it surrounds its own center. But its own center is in the interior of the 600-cell, not on its surface.
For n = 3 this quotient may be described as a solid torus with cross-section an equilateral triangle, with a twist; equivalently, as a triangular prism whose top and bottom faces are connected with a 1/3 twist (120°): the 3-dimensional interior corresponds to the points on the 3-torus where all 3 coordinates are distinct, the 2-dimensional ...