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  2. ♯P-completeness of 01-permanent - Wikipedia

    en.wikipedia.org/wiki/%E2%99%AFP-completeness_of...

    In order to prove that 01-Permanent is #P-hard, it is therefore sufficient to show that the number of satisfying assignments for a 3-CNF formula can be expressed succinctly as a function of the permanent of a matrix that contains only the values 0 and 1. This is usually accomplished in two steps:

  3. Coefficient of determination - Wikipedia

    en.wikipedia.org/wiki/Coefficient_of_determination

    An R 2 of 1 indicates that the regression predictions perfectly fit the data. Values of R 2 outside the range 0 to 1 occur when the model fits the data worse than the worst possible least-squares predictor (equivalent to a horizontal hyperplane at a height equal to the mean of the observed data). This occurs when a wrong model was chosen, or ...

  4. Equivalence of metrics - Wikipedia

    en.wikipedia.org/wiki/Equivalence_of_metrics

    Two metrics and on X are strongly or bilipschitz equivalent or uniformly equivalent if and only if there exist positive constants and such that, for every ,, (,) (,) (,).In contrast to the sufficient condition for topological equivalence listed above, strong equivalence requires that there is a single set of constants that holds for every pair of points in , rather than potentially different ...

  5. Elementary equivalence - Wikipedia

    en.wikipedia.org/wiki/Elementary_equivalence

    Two structures M and N of the same signature σ are elementarily equivalent if every first ... of Mathematics (3rd ed.), Elsevier, ISBN 978-0-444-88054-3 ...

  6. Pearson correlation coefficient - Wikipedia

    en.wikipedia.org/wiki/Pearson_correlation...

    (Here, φ is measured counterclockwise within the first quadrant formed around the lines' intersection point if r > 0, or counterclockwise from the fourth to the second quadrant if r < 0.) One can show [18] that if the standard deviations are equal, then r = sec φ − tan φ, where sec and tan are trigonometric functions.

  7. Norm (mathematics) - Wikipedia

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

    Because property (2.) implies () =, some authors replace property (3.) with the equivalent condition: for every , = if and only if = A seminorm on X {\displaystyle X} is a function p : X → R {\displaystyle p:X\to \mathbb {R} } that has properties (1.) and (2.) [ 6 ] so that in particular, every norm is also a seminorm (and thus also a ...

  8. Equivalence relation - Wikipedia

    en.wikipedia.org/wiki/Equivalence_relation

    For example, the natural numbers 2 and 6 have a common factor greater than 1, and 6 and 3 have a common factor greater than 1, but 2 and 3 do not have a common factor greater than 1. The empty relation R (defined so that aRb is never true) on a set X is vacuously symmetric and transitive; however, it is not reflexive (unless X itself is empty).

  9. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    A formula for computing the trigonometric identities for the one-third angle exists, but it requires finding the zeroes of the cubic equation 4x 3 − 3x + d = 0, where is the value of the cosine function at the one-third angle and d is the known value of the cosine function at the full angle.