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  2. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    A sphere of radius r has area element = ⁡. This can be found from the volume element in spherical coordinates with r held constant. [9] A sphere of any radius centered at zero is an integral surface of the following differential form: + + =

  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. Unit sphere - Wikipedia

    en.wikipedia.org/wiki/Unit_sphere

    In mathematics, a unit sphere is a sphere of unit radius: the set of points at Euclidean distance 1 from some center point in three-dimensional space. More generally, the unit n {\displaystyle n} -sphere is an n {\displaystyle n} -sphere of unit radius in ( n + 1 ) {\displaystyle (n+1)} - dimensional Euclidean space ; the unit circle is a ...

  5. List of centroids - Wikipedia

    en.wikipedia.org/wiki/List_of_centroids

    Quarter-circular area [2] ... Solid sphere: r = the radius of the sphere Solid hemisphere: r = the radius of the hemisphere ...

  6. Steradian - Wikipedia

    en.wikipedia.org/wiki/Steradian

    r is the radius of the sphere, h is the height of the cap, and; sr is the unit, steradian, sr = rad 2. Because the surface area A of a sphere is 4πr 2, the definition implies that a sphere subtends 4π steradians (≈ 12.56637 sr) at its centre, or that a steradian subtends 1/4π ≈ 0.07958 of a sphere.

  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. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    Here "area" means the area of the object when projected along the viewing direction. Any area on a sphere which is equal in area to the square of its radius, when observed from its center, subtends precisely one steradian. The solid angle of a sphere measured from any point in its interior is 4 π sr.

  9. Area - Wikipedia

    en.wikipedia.org/wiki/Area

    The formula for the surface area of a sphere was first obtained by Archimedes in his work On the Sphere and Cylinder. The formula is: [6] A = 4πr 2 (sphere), where r is the radius of the sphere. As with the formula for the area of a circle, any derivation of this formula inherently uses methods similar to calculus.