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  2. Tetrahedron - Wikipedia

    en.wikipedia.org/wiki/Tetrahedron

    A regular tetrahedron is a tetrahedron in which all ... of the 1st century Heron's formula for the area of a ... by an irregular triangulated surface, and irregular ...

  3. 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 ...

  4. List of formulas in elementary geometry - Wikipedia

    en.wikipedia.org/wiki/List_of_formulas_in...

    The basic quantities describing a sphere (meaning a 2-sphere, a 2-dimensional surface inside 3-dimensional space) will be denoted by the following variables r {\displaystyle r} is the radius, C = 2 π r {\displaystyle C=2\pi r} is the circumference (the length of any one of its great circles ),

  5. Platonic solid - Wikipedia

    en.wikipedia.org/wiki/Platonic_solid

    This follows from the spherical excess formula for a spherical polygon and the fact that the vertex figure of the polyhedron {p,q} is a regular q-gon. The solid angle of a face subtended from the center of a platonic solid is equal to the solid angle of a full sphere (4 π steradians) divided by the number of faces.

  6. Polyhedron - Wikipedia

    en.wikipedia.org/wiki/Polyhedron

    The surface area of a polyhedron is the sum of ... Simple families of solids may have simple formulas for their ... the rotation group for a regular tetrahedron; ...

  7. Regular polyhedron - Wikipedia

    en.wikipedia.org/wiki/Regular_polyhedron

    The tetrahedron, cube, and octahedron ... Abstract regular polytopes remain an active area of research. ... On a spherical surface, the regular polyhedron {2, ...

  8. Truncated tetrahedron - Wikipedia

    en.wikipedia.org/wiki/Truncated_tetrahedron

    Given the edge length .The surface area of a truncated tetrahedron is the sum of 4 regular hexagons and 4 equilateral triangles' area, and its volume is: [2] =, =.. The dihedral angle of a truncated tetrahedron between triangle-to-hexagon is approximately 109.47°, and that between adjacent hexagonal faces is approximately 70.53°.

  9. Uniform polyhedron - Wikipedia

    en.wikipedia.org/wiki/Uniform_polyhedron

    The octahedron is a regular polyhedron, and a triangular antiprism. The octahedron is also a rectified tetrahedron. Many polyhedra are repeated from different construction sources, and are colored differently. The Wythoff construction applies equally to uniform polyhedra and uniform tilings on the surface of a sphere, so