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  2. Tetrahedron - Wikipedia

    en.wikipedia.org/wiki/Tetrahedron

    The volume of a tetrahedron can be obtained in many ways. It can be given by using the formula of the pyramid's volume: =. where is the base' area and is the height from the base to the apex. This applies for each of the four choices of the base, so the distances from the apices to the opposite faces are inversely proportional to the areas of ...

  3. Elongated triangular pyramid - Wikipedia

    en.wikipedia.org/wiki/Elongated_triangular_pyramid

    An elongated triangular pyramid with edge length has a height, by adding the height of a regular tetrahedron and a triangular prism: [4] (+). Its surface area can be calculated by adding the area of all eight equilateral triangles and three squares: [2] (+), and its volume can be calculated by slicing it into a regular tetrahedron and a prism, adding their volume up: [2]: ((+)).

  4. Elongated triangular bipyramid - Wikipedia

    en.wikipedia.org/wiki/Elongated_triangular_bipyramid

    The surface area of an elongated triangular bipyramid is the sum of all polygonal face's area: six equilateral triangles and three squares. The volume of an elongated triangular bipyramid V {\displaystyle V} can be ascertained by slicing it off into two tetrahedrons and a regular triangular prism and then adding their volume.

  5. Pyramid (geometry) - Wikipedia

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

    The surface area is the total area of each polyhedra's faces. In the case of a pyramid, its surface area is the sum of the area of triangles and the area of the polygonal base. The volume of a pyramid is the one-third product of the base's area and the height.

  6. Area of a triangle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_triangle

    Euclid proved that the area of a triangle is half that of a parallelogram with the same base and height in his book Elements in 300 BCE. [1] In 499 CE Aryabhata, used this illustrated method in the Aryabhatiya (section 2.6). [2] Although simple, this formula is only useful if the height can be readily found, which is not always the case.

  7. Surface area - Wikipedia

    en.wikipedia.org/wiki/Surface_area

    A sphere of radius r has surface area 4πr 2.. The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies. [1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with ...

  8. Triangular bipyramid - Wikipedia

    en.wikipedia.org/wiki/Triangular_bipyramid

    A triangular bipyramid with regular faces is numbered as the twelfth Johnson solid . [10] It is an example of a composite polyhedron because it is constructed by attaching two regular tetrahedra. [11] [12] A triangular bipyramid's surface area is six times that of each triangle

  9. Pentagonal bipyramid - Wikipedia

    en.wikipedia.org/wiki/Pentagonal_bipyramid

    the dihedral angle of a pentagonal bipyramid between two adjacent triangles is that of a pentagonal pyramid, approximately 138.2°, and the dihedral angle of a pentagonal bipyramid with regular faces between two adjacent triangular faces, on the edge where two pyramids are attached, is 74.8°, obtained by summing the dihedral angle of a ...