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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 ...
The area of a regular polygon is half its perimeter multiplied by the distance from its center to its sides, and because the sequence tends to a circle, the corresponding formula–that the area is half the circumference times the radius–namely, A = 1 / 2 × 2πr × r, holds for a circle.
The curved surface area of the spherical segment bounded by two parallel disks is the difference of surface areas of their respective spherical caps. For a sphere of radius r {\displaystyle r} , and caps with heights h 1 {\displaystyle h_{1}} and h 2 {\displaystyle h_{2}} , the area is
The following is a list of centroids of various two-dimensional and three-dimensional objects. The centroid of an object in -dimensional space is the intersection of all hyperplanes that divide into two parts of equal moment about the hyperplane.
The surface area of the sphere of radius r is = which implies = By Gauss's law the flux is also Φ E = Q A ε 0 {\displaystyle \Phi _{E}={\frac {Q_{A}}{\varepsilon _{0}}}} finally equating the expression for Φ E gives the magnitude of the E -field at position r : E 4 π r 2 = Q A ε 0 ⇒ E = Q A 4 π ε 0 r 2 . {\displaystyle E4\pi r^{2 ...
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.
At any given radius r, [note 1] the incremental volume (δV) equals the product of the surface area at radius r (A(r)) and the thickness of a shell (δr): (). The total volume is the summation of all shell volumes: ().
The surface area of an ()-sphere with radius is and the volume of an - ball with radius is . For instance, the area is A 2 = 4 π r 2 {\displaystyle A_{2}=4\pi r^{2}} for the two-dimensional surface of the three-dimensional ball of radius r . {\displaystyle r.}