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  2. List of mathematical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_constants

    A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]

  3. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    is the number of collisions made (in ideal conditions, perfectly elastic with no friction) by an object of mass m initially at rest between a fixed wall and another object of mass b 2N m, when struck by the other object. [1] (This gives the digits of π in base b up to N digits past the radix point.)

  4. Area of a circle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_circle

    The circumference is 2 π r, and the area of a triangle is half the base times the height, yielding the area π r 2 for the disk. Prior to Archimedes, Hippocrates of Chios was the first to show that the area of a disk is proportional to the square of its diameter, as part of his quadrature of the lune of Hippocrates , [ 2 ] but did not identify ...

  5. List of physical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_constants

    Symbol Quantity Value [a] [b] Relative standard uncertainty Ref [1]; speed of light in vacuum : 299 792 458 m⋅s −1: 0 [2]Planck constant: 6.626 070 15 × 10 −34 J⋅Hz −1: 0 [3]= / reduced Planck constant

  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. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    Thus, in equation 4, the angle associated with the product is: arctan ⁡ a 1 b 2 + a 2 b 1 b 1 b 2 − a 1 a 2 {\displaystyle \arctan {\frac {a_{1}b_{2}+a_{2}b_{1}}{b_{1}b_{2}-a_{1}a_{2}}}} Note that this is the same expression as occurs in equation 3 .

  8. Inverse-square law - Wikipedia

    en.wikipedia.org/wiki/Inverse-square_law

    Since the surface area of a sphere of radius r is A = 4πr 2, the intensity I (power per unit area) of radiation at distance r is = =. The energy or intensity decreases (divided by 4) as the distance r is doubled; if measured in dB would decrease by 6.02 dB per doubling of distance. When referring to measurements of power quantities, a ratio ...

  9. Mathematical constant - Wikipedia

    en.wikipedia.org/wiki/Mathematical_constant

    The square root of 2 is equal to the length of the hypotenuse of a right-angled triangle with legs of length 1. The square root of 2, often known as root 2 or Pythagoras' constant, and written as √ 2, is the unique positive real number that, when multiplied by itself, gives the number 2. It is more precisely called the principal square root ...