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  2. Quaternion - Wikipedia

    en.wikipedia.org/wiki/Quaternion

    Quaternions are also used in one of the proofs of Lagrange's four-square theorem in number theory, which states that every nonnegative integer is the sum of four integer squares. As well as being an elegant theorem in its own right, Lagrange's four square theorem has useful applications in areas of mathematics outside number theory, such as ...

  3. List of unsolved problems in mathematics - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Lander, Parkin, and Selfridge conjecture: if the sum of -th powers of positive integers is equal to a different sum of -th powers of positive integers, then +. Lemoine's conjecture : all odd integers greater than 5 {\displaystyle 5} can be represented as the sum of an odd prime number and an even semiprime .

  4. Number theory - Wikipedia

    en.wikipedia.org/wiki/Number_theory

    This includes Fermat's little theorem (generalised by Euler to non-prime moduli); the fact that = + if and only if ; initial work towards a proof that every integer is the sum of four squares (the first complete proof is by Joseph-Louis Lagrange (1770), soon improved by Euler himself [55]); the lack of non-zero integer solutions to ...

  5. Hexadecimal - Wikipedia

    en.wikipedia.org/wiki/Hexadecimal

    Hexadecimal (also known as base-16 or simply hex) is a positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbols, hexadecimal uses sixteen distinct symbols, most often the symbols "0"–"9" to represent values 0 to 9 and "A"–"F" to represent values from ten to fifteen.

  6. Savitzky–Golay filter - Wikipedia

    en.wikipedia.org/wiki/Savitzky–Golay_filter

    When the data points are equally spaced, an analytical solution to the least-squares equations can be found. [2] This solution forms the basis of the convolution method of numerical smoothing and differentiation. Suppose that the data consists of a set of n points (x j, y j) (j = 1, ..., n), where x j is an independent variable and y j is a

  7. Octal - Wikipedia

    en.wikipedia.org/wiki/Octal

    0.5 × 8 = 4.0 = 4 + 0 Therefore, 0.1640625 10 = 0.124 8 . These two methods can be combined to handle decimal numbers with both integer and fractional parts, using the first on the integer part and the second on the fractional part.

  8. Proof by infinite descent - Wikipedia

    en.wikipedia.org/wiki/Proof_by_infinite_descent

    In mathematics, a proof by infinite descent, also known as Fermat's method of descent, is a particular kind of proof by contradiction [1] used to show that a statement cannot possibly hold for any number, by showing that if the statement were to hold for a number, then the same would be true for a smaller number, leading to an infinite descent and ultimately a contradiction. [2]

  9. Solar irradiance - Wikipedia

    en.wikipedia.org/wiki/Solar_irradiance

    In fact, under clear skies a solar panel placed horizontally at the north or south pole at midsummer receives more sunlight over 24 hours (cosine of angle of incidence equal to sin(23.5°) or about 0.40) than a horizontal panel at the equator at the equinox (average cosine equal to 1/ π or about 0.32).