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  2. Error function - Wikipedia

    en.wikipedia.org/wiki/Error_function

    This directly results from the fact that the integrand e −t 2 is an even function (the antiderivative of an even function which is zero at the origin is an odd function and vice versa).

  3. Solution of triangles - Wikipedia

    en.wikipedia.org/wiki/Solution_of_triangles

    If D = 1, a unique solution exists: γ = 90°, i.e., the triangle is right-angled. If D < 1 two alternatives are possible. If b ≥ c, then β ≥ γ (the larger side corresponds to a larger angle). Since no triangle can have two obtuse angles, γ is an acute angle and the solution γ = arcsin D is unique.

  4. Letter frequency - Wikipedia

    en.wikipedia.org/wiki/Letter_frequency

    The California Job Case was a compartmentalized box for printing in the 19th century, sizes corresponding to the commonality of letters. The frequency of letters in text has been studied for use in cryptanalysis, and frequency analysis in particular, dating back to the Arab mathematician al-Kindi (c. AD 801–873 ), who formally developed the method (the ciphers breakable by this technique go ...

  5. Low emissivity - Wikipedia

    en.wikipedia.org/wiki/Low_emissivity

    As it is an opaque material, the remaining 10 percent must be reflected. Conversely, a low-e material such as aluminum foil has a thermal emissivity/absorptance value of 0.03 and as an opaque material, the thermal reflectance value must be 1.0 - 0.03 =0.97, meaning it reflects 97 percent of radiant thermal energy. Low-emissivity building ...

  6. Symmetric mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Symmetric_mean_absolute...

    Provided the data are strictly positive, a better measure of relative accuracy can be obtained based on the log of the accuracy ratio: log(F t / A t) This measure is easier to analyze statistically and has valuable symmetry and unbiasedness properties.

  7. Orbital eccentricity - Wikipedia

    en.wikipedia.org/wiki/Orbital_eccentricity

    For elliptical orbits, a simple proof shows that ⁡ yields the projection angle of a perfect circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury (e = 0.2056), one must simply calculate the inverse sine to find the projection angle of 11.86 degrees. Then, tilting any circular object by that angle ...

  8. Orders of magnitude (energy) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(energy)

    List of orders of magnitude for energy; Factor (joules) SI prefix Value Item 10 −34: 6.626 × 10 −34 J: Energy of a photon with a frequency of 1 hertz. [1]8 × 10 −34 J: Average kinetic energy of translational motion of a molecule at the lowest temperature reached (38 picokelvin [2] as of 2021)

  9. Emissivity - Wikipedia

    en.wikipedia.org/wiki/Emissivity

    L e,Ω,λ ° is the spectral radiance in wavelength of a black body at the same temperature as that surface. Hemispherical emissivity can also be expressed as a weighted average of the directional spectral emissivities as described in textbooks on "radiative heat transfer".