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  2. Metric projection - Wikipedia

    en.wikipedia.org/wiki/Metric_projection

    If M is non-empty compact set, then the metric projection p M is upper semi-continuous, but might not be lower semi-continuous. But if X is a normed space and M is a finite-dimensional Chebyshev set, then p M is continuous. [citation needed] Moreover, if X is a Hilbert space and M is closed and convex, then p M is Lipschitz continuous with ...

  3. Metric space - Wikipedia

    en.wikipedia.org/wiki/Metric_space

    A function : is continuous if for every point x in M 1 and every ε > 0 there exists δ > 0 such that for all y in M 1 we have (,) < ((), ()) <. A homeomorphism is a continuous bijection whose inverse is also continuous; if there is a homeomorphism between M 1 and M 2 , they are said to be homeomorphic .

  4. Integer-valued function - Wikipedia

    en.wikipedia.org/wiki/Integer-valued_function

    In mathematics, an integer-valued function is a function whose values are integers.In other words, it is a function that assigns an integer to each member of its domain.. The floor and ceiling functions are examples of integer-valued functions of a real variable, but on real numbers and, generally, on (non-disconnected) topological spaces integer-valued functions are not especially useful.

  5. Floor and ceiling functions - Wikipedia

    en.wikipedia.org/wiki/Floor_and_ceiling_functions

    At points of discontinuity, a Fourier series converges to a value that is the average of its limits on the left and the right, unlike the floor, ceiling and fractional part functions: for y fixed and x a multiple of y the Fourier series given converges to y/2, rather than to x mod y = 0. At points of continuity the series converges to the true ...

  6. List of mathematical functions - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_functions

    Dirac delta function: everywhere zero except for x = 0; total integral is 1. Not a function but a distribution, but sometimes informally referred to as a function, particularly by physicists and engineers. Dirichlet function: is an indicator function that matches 1 to rational numbers and 0 to irrationals. It is nowhere continuous.

  7. Map (mathematics) - Wikipedia

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

    A map is a function, as in the association of any of the four colored shapes in X to its color in Y. In mathematics, a map or mapping is a function in its general sense. [1] These terms may have originated as from the process of making a geographical map: mapping the Earth surface to a sheet of paper. [2]

  8. Signed distance function - Wikipedia

    en.wikipedia.org/wiki/Signed_distance_function

    The function has positive values at points x inside Ω, it decreases in value as x approaches the boundary of Ω where the signed distance function is zero, and it takes negative values outside of Ω. [1] However, the alternative convention is also sometimes taken instead (i.e., negative inside Ω and positive outside). [2]

  9. Square metre - Wikipedia

    en.wikipedia.org/wiki/Square_metre

    Comparison of 1 square metre with some Imperial and metric units of area. The square metre (international spelling as used by the International Bureau of Weights and Measures) or square meter (American spelling) is the unit of area in the International System of Units (SI) with symbol m 2. [1] It is the area of a square with sides one metre in ...