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  2. Total acid number - Wikipedia

    en.wikipedia.org/wiki/Total_Acid_Number

    The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. [1] It is an important quality measurement of crude oil. The TAN value indicates to the crude oil refinery the potential of corrosion problems.

  3. Euler's formula - Wikipedia

    en.wikipedia.org/wiki/Euler's_formula

    Many texts write φ = tan −1 ⁠ y / x ⁠ instead of φ = atan2(y, x), but the first equation needs adjustment when x ≤ 0. This is because for any real x and y , not both zero, the angles of the vectors ( x , y ) and (− x , − y ) differ by π radians, but have the identical value of tan φ = ⁠ y / x ⁠ .

  4. Theta function - Wikipedia

    en.wikipedia.org/wiki/Theta_function

    There are several closely related functions called Jacobi theta functions, and many different and incompatible systems of notation for them. One Jacobi theta function (named after Carl Gustav Jacob Jacobi) is a function defined for two complex variables z and τ, where z can be any complex number and τ is the half-period ratio, confined to the upper half-plane, which means it has a positive ...

  5. Floor and ceiling functions - Wikipedia

    en.wikipedia.org/wiki/Floor_and_ceiling_functions

    Given real numbers x and y, integers m and n and the set of integers, floor and ceiling may be defined by the equations ⌊ ⌋ = {}, ⌈ ⌉ = {}. Since there is exactly one integer in a half-open interval of length one, for any real number x, there are unique integers m and n satisfying the equation

  6. Relative permittivity - Wikipedia

    en.wikipedia.org/wiki/Relative_permittivity

    Temperature dependence of the relative static permittivity of water. The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum.

  7. Tan-1 - Wikipedia

    en.wikipedia.org/wiki/Tan-1

    Tan-1, TAN-1, tan-1, or tan 1 may refer to: tan 1 y = tan 1 ( x ), sometimes interpreted as arctan( x ) or arctangent of x , the compositional inverse of the trigonometric function tangent (see below for ambiguity)

  8. Radius of convergence - Wikipedia

    en.wikipedia.org/wiki/Radius_of_convergence

    Two cases arise: The first case is theoretical: when you know all the coefficients then you take certain limits and find the precise radius of convergence.; The second case is practical: when you construct a power series solution of a difficult problem you typically will only know a finite number of terms in a power series, anywhere from a couple of terms to a hundred terms.

  9. Multiplicative inverse - Wikipedia

    en.wikipedia.org/wiki/Multiplicative_inverse

    The reciprocal function: y = 1/x.For every x except 0, y represents its multiplicative inverse. The graph forms a rectangular hyperbola.. In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by 1/x or x −1, is a number which when multiplied by x yields the multiplicative identity, 1.