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  2. Del in cylindrical and spherical coordinates - Wikipedia

    en.wikipedia.org/wiki/Del_in_cylindrical_and...

    This article uses the standard notation ISO 80000-2, which supersedes ISO 31-11, for spherical coordinates (other sources may reverse the definitions of θ and φ): . The polar angle is denoted by [,]: it is the angle between the z-axis and the radial vector connecting the origin to the point in question.

  3. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    (Note the 'full' rotation, or inclination, from the zenith–axis to the y–axis is 90°). Just as the two-dimensional Cartesian coordinate system is useful—has a wide set of applications—on a planar surface, a two-dimensional spherical coordinate system is useful on the surface of a sphere.

  4. Free probability - Wikipedia

    en.wikipedia.org/wiki/Free_probability

    The "freeness" or free independence property is the analogue of the classical notion of independence, and it is connected with free products. This theory was initiated by Dan Voiculescu around 1986 in order to attack the free group factors isomorphism problem, an important unsolved problem in the theory of operator algebras .

  5. Free algebra - Wikipedia

    en.wikipedia.org/wiki/Free_algebra

    Since rings may be regarded as Z-algebras, a free ring on E can be defined as the free algebra Z E . Over a field, the free algebra on n indeterminates can be constructed as the tensor algebra on an n-dimensional vector space. For a more general coefficient ring, the same construction works if we take the free module on n generators.

  6. Inclusion–exclusion principle - Wikipedia

    en.wikipedia.org/wiki/Inclusion–exclusion...

    Venn diagram showing the union of sets A and B as everything not in white. In combinatorics, the inclusion–exclusion principle is a counting technique which generalizes the familiar method of obtaining the number of elements in the union of two finite sets; symbolically expressed as

  7. Plancherel theorem - Wikipedia

    en.wikipedia.org/wiki/Plancherel_theorem

    In mathematics, the Plancherel theorem (sometimes called the Parseval–Plancherel identity) is a result in harmonic analysis, proven by Michel Plancherel in 1910. It is a generalization of Parseval's theorem; often used in the fields of science and engineering, proving the unitarity of the Fourier transform.

  8. The Order of Time (book) - Wikipedia

    en.wikipedia.org/wiki/The_Order_of_Time_(book)

    Book Marks reported that the book received "positive" reviews based on 7 critic reviews with 2 being "rave" and 5 being "positive". [7] Writing for The Guardian, Ian Thomson praised the "lucid" writing, translation, and compared it to Seven Brief Lessons on Physics, describing it as a "a deeper, more abstruse meditation" but "jargon-free". [2]

  9. Rodrigues' rotation formula - Wikipedia

    en.wikipedia.org/wiki/Rodrigues'_rotation_formula

    A detailed historical analysis in 1989 concluded that the formula should be attributed to Euler, and recommended calling it "Euler's finite rotation formula." [ 1 ] This proposal has received notable support, [ 2 ] but some others have viewed the formula as just one of many variations of the Euler–Rodrigues formula , thereby crediting both.