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The volume of the unit ball in Euclidean -space, and the surface area of the unit sphere, appear in many important formulas of analysis. The volume of the unit n {\displaystyle n} -ball, which we denote V n , {\displaystyle V_{n},} can be expressed by making use of the gamma function .
Volumes of balls in dimensions 0 through 25; unit ball in red. In geometry, a ball is a region in a space comprising all points within a fixed distance, called the radius, from a given point; that is, it is the region enclosed by a sphere or hypersphere. An n-ball is a ball in an n-dimensional Euclidean space.
In particular, a ball (open or closed) always includes p itself, since the definition requires r > 0. A unit ball (open or closed) is a ball of radius 1. A ball in a general metric space need not be round. For example, a ball in real coordinate space under the Chebyshev distance is a hypercube, and a ball under the taxicab distance is a cross ...
Area#Area formulas – Size of a two-dimensional surface; Perimeter#Formulas – Path that surrounds an area; List of second moments of area; List of surface-area-to-volume ratios – Surface area per unit volume; List of surface area formulas – Measure of a two-dimensional surface; List of trigonometric identities
The given formula is for the plane passing through the center of mass, which coincides with the geometric center of the cylinder. If the xy plane is at the base of the cylinder, i.e. offset by d = h 2 , {\displaystyle d={\frac {h}{2}},} then by the parallel axis theorem the following formula applies:
The unit for radial distance is usually determined by the context, as occurs in applications of the 'unit sphere', see applications. When the system is used to designate physical three-space, it is customary to assign positive to azimuth angles measured in the counterclockwise sense from the reference direction on the reference plane—as seen ...
This formula is valid only for configurations that satisfy < < and () <. If sphere 2 is very large such that r 2 ≫ r 1 {\displaystyle r_{2}\gg r_{1}} , hence d ≫ h {\displaystyle d\gg h} and r 2 ≈ d {\displaystyle r_{2}\approx d} , which is the case for a spherical cap with a base that has a negligible curvature, the above equation is ...
An alternative given by Marsaglia is to uniformly randomly select a point = (,, …,) in the unit n-cube by sampling each independently from the uniform distribution over (,) , computing as above, and rejecting the point and resampling if (i.e., if the point is not in the -ball), and when a point in ...