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  2. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    where A is the area of a squircle with minor radius r, is the gamma function. A = ( k + 1 ) ( k + 2 ) π r 2 {\displaystyle A=(k+1)(k+2)\pi r^{2}} where A is the area of an epicycloid with the smaller circle of radius r and the larger circle of radius kr ( k ∈ N {\displaystyle k\in \mathbb {N} } ), assuming the initial point lies on the ...

  3. Equivalent radius - Wikipedia

    en.wikipedia.org/wiki/Equivalent_radius

    US hat size is the circumference of the head, measured in inches, divided by pi, rounded to the nearest 1/8 inch. This corresponds to the 1D mean diameter. [1] Diameter at breast height is the circumference of tree trunk, measured at height of 4.5 feet, divided by pi. This corresponds to the 1D mean diameter.

  4. List of second moments of area - Wikipedia

    en.wikipedia.org/wiki/List_of_second_moments_of_area

    A filled ellipse whose radius along the x-axis is a and whose radius along the y-axis is b I x = π 4 a b 3 I y = π 4 a 3 b {\displaystyle {\begin{aligned}I_{x}&={\frac {\pi }{4}}ab^{3}\\[3pt]I_{y}&={\frac {\pi }{4}}a^{3}b\end{aligned}}}

  5. Pi - Wikipedia

    en.wikipedia.org/wiki/Pi

    The volume of a sphere with radius r is ⁠ 4 / 3 ⁠ πr 3. The surface area of a sphere with radius r is 4πr 2. Some of the formulae above are special cases of the volume of the n-dimensional ball and the surface area of its boundary, the (n−1)-dimensional sphere, given below. Apart from circles, there are other curves of constant width.

  6. Area of a circle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_circle

    A History of Pi; In culture; ... This suggests that the area of a disk is half the circumference of its bounding circle times the radius. [3] ... 3.1427182 4: 96: 6 ...

  7. Euler's identity - Wikipedia

    en.wikipedia.org/wiki/Euler's_identity

    is pi, the ratio of the circumference of a circle to its diameter. Euler's identity is named after the Swiss mathematician Leonhard Euler . It is a special case of Euler's formula e i x = cos ⁡ x + i sin ⁡ x {\displaystyle e^{ix}=\cos x+i\sin x} when evaluated for x = π {\displaystyle x=\pi } .

  8. List of centroids - Wikipedia

    en.wikipedia.org/wiki/List_of_centroids

    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.

  9. Approximations of π - Wikipedia

    en.wikipedia.org/wiki/Approximations_of_π

    The Chinese mathematician Liu Hui in 263 CE computed π to between 3.141 024 and 3.142 708 by inscribing a 96-gon and 192-gon; the average of these two values is 3.141 866 (accuracy 9·10 −5). He also suggested that 3.14 was a good enough approximation for practical purposes.