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  2. Circle packing theorem - Wikipedia

    en.wikipedia.org/wiki/Circle_packing_theorem

    A stronger form of the circle packing theorem asserts that any polyhedral graph and its dual graph can be represented by two circle packings, such that the two tangent circles representing a primal graph edge and the two tangent circles representing the dual of the same edge always have their tangencies at right angles to each other at the same ...

  3. Trigonometry - Wikipedia

    en.wikipedia.org/wiki/Trigonometry

    In the 2nd century AD, the Greco-Egyptian astronomer Ptolemy (from Alexandria, Egypt) constructed detailed trigonometric tables (Ptolemy's table of chords) in Book 1, chapter 11 of his Almagest. [11] Ptolemy used chord length to define his trigonometric functions, a minor difference from the sine convention we use today. [12] (The value we call ...

  4. Legendre transformation - Wikipedia

    en.wikipedia.org/wiki/Legendre_transformation

    The function () is defined on the interval [,].For a given , the difference () takes the maximum at ′.Thus, the Legendre transformation of () is () = ′ (′).. In mathematics, the Legendre transformation (or Legendre transform), first introduced by Adrien-Marie Legendre in 1787 when studying the minimal surface problem, [1] is an involutive transformation on real-valued functions that are ...

  5. Curvilinear coordinates - Wikipedia

    en.wikipedia.org/wiki/Curvilinear_coordinates

    Tangent plane element: If x(λ 1, λ 2) parametrizes a surface S in Cartesian coordinates, then the following cross product of tangent vectors is a normal vector to S with the magnitude of infinitesimal plane element, in curvilinear coordinates. Using the above result,

  6. Inverse hyperbolic functions - Wikipedia

    en.wikipedia.org/wiki/Inverse_hyperbolic_functions

    Graphs of the inverse hyperbolic functions The hyperbolic functions sinh, cosh, and tanh with respect to a unit hyperbola are analogous to circular functions sin, cos, tan with respect to a unit circle. The argument to the hyperbolic functions is a hyperbolic angle measure.

  7. Analytic geometry - Wikipedia

    en.wikipedia.org/wiki/Analytic_geometry

    In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point. Informally, it is a line through a pair of infinitely close points on the curve.

  8. Inversive geometry - Wikipedia

    en.wikipedia.org/wiki/Inversive_geometry

    In geometry, inversive geometry is the study of inversion, a transformation of the Euclidean plane that maps circles or lines to other circles or lines and that preserves the angles between crossing curves. Many difficult problems in geometry become much more tractable when an inversion is applied.

  9. Contact (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Contact_(mathematics)

    Contact transformations are related changes of coordinates, of importance in classical mechanics. See also Legendre transformation . Contact between manifolds is often studied in singularity theory , where the type of contact are classified, these include the A series ( A 0 : crossing, A 1 : tangent, A 2 : osculating, ...) and the umbilic or D ...