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The cross-sectional area (′) of an object when viewed from a particular angle is the total area of the orthographic projection of the object from that angle. For example, a cylinder of height h and radius r has A ′ = π r 2 {\displaystyle A'=\pi r^{2}} when viewed along its central axis, and A ′ = 2 r h {\displaystyle A'=2rh} when viewed ...
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.
In geometry, a polyhedron (pl.: polyhedra or polyhedrons; from Greek πολύ (poly-) 'many' and ἕδρον (-hedron) 'base, seat') is a three-dimensional figure with flat polygonal faces, straight edges and sharp corners or vertices. A convex polyhedron is a polyhedron that bounds a convex set.
The rhombic dodecahedron forms the maximal cross-section of a 24-cell, and also forms the hull of its vertex-first parallel projection into three dimensions. The rhombic dodecahedron can be decomposed into six congruent (but non-regular) square dipyramids meeting at a single vertex in the center; these form the images of six pairs of the 24 ...
This resulting polyhedron has six squares and eight hexagons, leaving out six square pyramids. Setting the edge length of the regular octahedron equal to 3 a {\displaystyle 3a} , it follows that the length of each edge of a square pyramid (to be removed) is a {\displaystyle a} (the square pyramid is has four equilateral triangles as faces, the ...
A square bipyramid is a bipyramid constructed by attaching two square pyramids base-to-base. These pyramids cover their square bases, so the resulting polyhedron has eight triangular faces. [1] A square bipyramid is said to be right if the square pyramids are symmetrically regular and both of their apices are on the line passing through the ...
A polyhedron comprising an n-sided polygonal base, a second base translated and rotated.sides]] of the two bases square antiprism: Bipyramid: A polyhedron comprising an n-sided polygonal center with two apexes. triangular bipyramid: Trapezohedron: A polyhedron with 2n kite faces around an axis, with half offsets tetragonal trapezohedron: Cone
In geometry, a uniform polyhedron has regular polygons as faces and is vertex-transitive—there is an isometry mapping any vertex onto any other. It follows that all vertices are congruent . Uniform polyhedra may be regular (if also face- and edge-transitive ), quasi-regular (if also edge-transitive but not face-transitive), or semi-regular ...