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  2. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    where C is the circumference of a circle, d is the diameter, and r is the radius. More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width. = where A is the area of a circle. More generally, =

  3. Area of a circle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_circle

    Let C bisect the arc from A to B, and let C′ be the point opposite C on the circle. Thus the length of CA is s 2n, the length of C′A is c 2n, and C′CA is itself a right triangle on diameter CC. Because C bisects the arc from A to B, CC perpendicularly bisects the chord from A to B, say at P. Triangle C′AP is thus a right triangle ...

  4. Spherical wedge - Wikipedia

    en.wikipedia.org/wiki/Spherical_wedge

    Beman (2008) [2] remarks that "a spherical wedge is to the sphere of which it is a part as the angle of the wedge is to a perigon." A spherical wedge of α = π radians (180°) is called a hemisphere, while a spherical wedge of α = 2 π radians (360°) constitutes a complete ball.

  5. 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.

  6. List of mathematical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_constants

    For a lattice L in Euclidean space R n with unit covolume, i.e. vol(R n /L) = 1, let λ 1 (L) denote the least length of a nonzero element of L. Then √γ n n is the maximum of λ 1 (L) over all such lattices L. 1822 to 1901 Hafner–Sarnak–McCurley constant [118]

  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. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    F. C. M. Størmer (1896). Two equations are used so that one can check they both give the same result; it is helpful if the equations used to cross-check the result reuse some of the arctangent arguments (note the reuse of 57 and 239 above), so that the process can be simplified by only computing them once, but not all of them, in order to ...

  9. Pi - Wikipedia

    en.wikipedia.org/wiki/Pi

    The number π (/ p aɪ / ⓘ; spelled out as "pi") is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter.It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining π, to avoid relying on the definition of the length of a curve.