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  2. Three-dimensional space - Wikipedia

    en.wikipedia.org/wiki/Three-dimensional_space

    Another type of sphere arises from a 4-ball, whose three-dimensional surface is the 3-sphere: points equidistant to the origin of the euclidean space R 4. If a point has coordinates, P ( x , y , z , w ) , then x 2 + y 2 + z 2 + w 2 = 1 characterizes those points on the unit 3-sphere centered at the origin.

  3. n-sphere - Wikipedia

    en.wikipedia.org/wiki/N-sphere

    The surface area, or properly the ⁠ ⁠-dimensional volume, of the ⁠ ⁠-sphere at the boundary of the ⁠ (+) ⁠-ball of radius ⁠ ⁠ is related to the volume of the ball by the differential equation

  4. 3-sphere - Wikipedia

    en.wikipedia.org/wiki/3-sphere

    Direct projection of 3-sphere into 3D space and covered with surface grid, showing structure as stack of 3D spheres (2-spheres) In mathematics, a hypersphere or 3-sphere is a 4-dimensional analogue of a sphere, and is the 3-dimensional n-sphere. In 4-dimensional Euclidean space, it is the set of points equidistant from a fixed central point.

  5. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    The ordinary sphere is a 2-sphere, because it is a 2-dimensional surface which is embedded in 3-dimensional space. In topology , the n -sphere is an example of a compact topological manifold without boundary .

  6. Volume of an n-ball - Wikipedia

    en.wikipedia.org/wiki/Volume_of_an_n-ball

    Surface areas of hyperspheres in dimensions 0 through 25. Let A n − 1 (R) denote the hypervolume of the (n − 1)-sphere of radius R. The (n − 1)-sphere is the (n − 1)-dimensional boundary (surface) of the n-dimensional ball of radius R, and the sphere's hypervolume and the ball's hypervolume are related by:

  7. Steradian - Wikipedia

    en.wikipedia.org/wiki/Steradian

    A steradian can be defined as the solid angle subtended at the centre of a unit sphere by a unit area (of any shape) on its surface. For a general sphere of radius r, any portion of its surface with area A = r 2 subtends one steradian at its centre. [3] A solid angle in the form of a circular cone is related to the area it cuts out of a sphere:

  8. Spherical geometry - Wikipedia

    en.wikipedia.org/wiki/Spherical_geometry

    The sphere can be studied either extrinsically as a surface embedded in 3-dimensional Euclidean space ... Variae speculationes super area triangulorum sphaericorum ...

  9. Area - Wikipedia

    en.wikipedia.org/wiki/Area

    The area of a plane region or plane area refers to the area of a shape or planar lamina, while surface area refers to the area of an open surface or the boundary of a three-dimensional object. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint ...