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self-dual. Net. 3D model of a regular tetrahedron. In geometry, a tetrahedron ( pl.: tetrahedra or tetrahedrons ), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertices. The tetrahedron is the simplest of all the ordinary convex polyhedra.
Pyramid. Pyramid of Khafre, Egypt, built c. 2600 BC. A pyramid (from Ancient Greek πυραμίς (puramís) 'pyramid') [ 1][ 2] is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense.
A pyramid is a polyhedron that may be formed by connecting a polygonal base and a point, called the apex. Each base edge and apex form an isosceles triangle, called a lateral face. [7] The edges connected from the polygonal base's vertices to the apex are called lateral edges. [8] Historically, the definition of a pyramid has been described by ...
Triangular bipyramid. In geometry, a triangular prism or trigonal prism[ 1] is a prism with 2 triangular bases. If the edges pair with each triangle's vertex and if they are perpendicular to the base, it is a right triangular prism. A right triangular prism may be both semiregular and uniform . The triangular prism can be used in constructing ...
Triangular bipyramid. In geometry, the triangular bipyramid is the hexahedron with six triangular faces, constructed by attaching two tetrahedra face-to-face. The same shape is also called the triangular dipyramid [1] [2] or trigonal bipyramid. [3] If these tetrahedra are regular, all faces of triangular bipyramid are equilateral.
Egyptian pyramids. Coordinates: 29°58′21″N 31°07′42″E. A view of the Giza pyramid complex from the plateau to the south of the complex. From left to right, the three largest are: the Pyramid of Menkaure, the Pyramid of Khafre and the Great Pyramid of Giza. The three smaller pyramids in the foreground are subsidiary structures ...
The elongated triangular bipyramid is constructed from a triangular prism by attaching two tetrahedrons onto its bases, a process known as the elongation. [1] These tetrahedrons cover the triangular faces so that the resulting polyhedron has nine faces (six of them are equilateral triangles and three of them are squares), fifteen edges, and eight vertices. [2]
The elongated triangular pyramid is constructed from a triangular prism by attaching regular tetrahedron onto one of its bases, a process known as elongation. [1] The tetrahedron covers an equilateral triangle, replacing it with three other equilateral triangles, so that the resulting polyhedron has four equilateral triangles and three squares ...