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  2. Cone - Wikipedia

    en.wikipedia.org/wiki/Cone

    The lateral surface area of a right circular cone is = where is the radius of the circle at the bottom of the cone and is the slant height of the cone. [4] The surface area of the bottom circle of a cone is the same as for any circle, . Thus, the total surface area of a right circular cone can be expressed as each of the following:

  3. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    Dimension. 1 {\displaystyle 1} In geometry, a solid angle (symbol: Ω) is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point. The point from which the object is viewed is called the apex of the solid ...

  4. 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 ...

  5. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    Sphere. A sphere (from Greek σφαῖρα, sphaîra) [ 1] is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. Formally, a sphere is the set of points that are all at the same distance r from a given point in three-dimensional space. [ 2]

  6. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation . An ellipsoid is a quadric surface ; that is, a surface that may be defined as the zero set of a polynomial of degree two in three variables. Among quadric surfaces, an ellipsoid is ...

  7. Umbra, penumbra and antumbra - Wikipedia

    en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra

    An observer within the umbra experiences a total occultation. The umbra of a round body occluding a round light source forms a right circular cone. When viewed from the cone's apex, the two bodies appear the same size. The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth: 384,402 km (238,856 mi).

  8. Spherical sector - Wikipedia

    en.wikipedia.org/wiki/Spherical_sector

    In geometry, a spherical sector, [ 1] also known as a spherical cone, [ 2] is a portion of a sphere or of a ball defined by a conical boundary with apex at the center of the sphere. It can be described as the union of a spherical cap and the cone formed by the center of the sphere and the base of the cap. It is the three-dimensional analogue of ...

  9. Hypercone - Wikipedia

    en.wikipedia.org/wiki/Hypercone

    In geometry, a hypercone (or spherical cone) is the figure in the 4-dimensional Euclidean space represented by the equation. It is a quadric surface, and is one of the possible 3- manifolds which are 4-dimensional equivalents of the conical surface in 3 dimensions. It is also named "spherical cone" because its intersections with hyperplanes ...