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  2. Curvilinear coordinates - Wikipedia

    en.wikipedia.org/wiki/Curvilinear_coordinates

    Consequently, a general curvilinear coordinate system has two sets of basis vectors for every point: {b 1, b 2, b 3} is the contravariant basis, and {b 1, b 2, b 3} is the covariant (a.k.a. reciprocal) basis. The covariant and contravariant basis vectors types have identical direction for orthogonal curvilinear coordinate systems, but as usual ...

  3. Divergence - Wikipedia

    en.wikipedia.org/wiki/Divergence

    A point at which the flux is outgoing has positive divergence, and is often called a "source" of the field. A point at which the flux is directed inward has negative divergence, and is often called a "sink" of the field. The greater the flux of field through a small surface enclosing a given point, the greater the value of divergence at that point.

  4. Herfindahl–Hirschman index - Wikipedia

    en.wikipedia.org/wiki/Herfindahl–Hirschman_index

    Named after economists Orris C. Herfindahl and Albert O. Hirschman, it is an economic concept widely applied in competition law, antitrust regulation, [1] and technology management. [2] HHI has continued to be used by antitrust authorities, primarily to evaluate and understand how mergers will affect their associated markets. [3]

  5. Section formula - Wikipedia

    en.wikipedia.org/wiki/Section_formula

    In coordinate geometry, the Section formula is a formula used to find the ratio in which a line segment is divided by a point internally or externally. [1] It is used to find out the centroid, incenter and excenters of a triangle. In physics, it is used to find the center of mass of systems, equilibrium points, etc. [2] [3] [4] [5]

  6. Jacobian matrix and determinant - Wikipedia

    en.wikipedia.org/wiki/Jacobian_matrix_and...

    This means that the rank at the critical point is lower than the rank at some neighbour point. In other words, let k be the maximal dimension of the open balls contained in the image of f; then a point is critical if all minors of rank k of f are zero. In the case where m = n = k, a point is critical if the Jacobian determinant is zero.

  7. Antiderivative - Wikipedia

    en.wikipedia.org/wiki/Antiderivative

    The slope field of () = +, showing three of the infinitely many solutions that can be produced by varying the arbitrary constant c.. In calculus, an antiderivative, inverse derivative, primitive function, primitive integral or indefinite integral [Note 1] of a continuous function f is a differentiable function F whose derivative is equal to the original function f.

  8. Five-point stencil - Wikipedia

    en.wikipedia.org/wiki/Five-point_stencil

    An illustration of the five-point stencil in one and two dimensions (top, and bottom, respectively). In numerical analysis, given a square grid in one or two dimensions, the five-point stencil of a point in the grid is a stencil made up of the point itself together with its four "neighbors".

  9. Riemann sum - Wikipedia

    en.wikipedia.org/wiki/Riemann_sum

    Middle Riemann sum of x ↦ x 3 over [0, 2] using 4 subintervals For the midpoint rule, the function is approximated by its values at the midpoints of the subintervals. This gives f ( a + Δ x /2) for the first subinterval, f ( a + 3Δ x /2) for the next one, and so on until f ( b − Δ x /2) .