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  2. List of trigonometric identities - Wikipedia

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

    The product-to-sum identities [28] or prosthaphaeresis formulae can be proven by expanding their right-hand sides using the angle addition theorems. Historically, the first four of these were known as Werner's formulas, after Johannes Werner who used them for astronomical calculations. [29]

  3. Distribution of the product of two random variables - Wikipedia

    en.wikipedia.org/wiki/Distribution_of_the...

    The product is one type of algebra for random variables: Related to the product distribution are the ratio distribution, sum distribution (see List of convolutions of probability distributions) and difference distribution. More generally, one may talk of combinations of sums, differences, products and ratios.

  4. Plethystic exponential - Wikipedia

    en.wikipedia.org/wiki/Plethystic_exponential

    Some basic examples are: ... The plethystic exponential can be used to provide innumerous product-sum identities. This is a consequence of a product formula for ...

  5. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total.Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  6. Summation by parts - Wikipedia

    en.wikipedia.org/wiki/Summation_by_parts

    Summation by parts is frequently used to prove Abel's theorem and Dirichlet's test. One can also use this technique to prove Abel's test: If is a convergent series, and a bounded monotone sequence, then = = converges. Proof of Abel's test.

  7. Pythagorean theorem - Wikipedia

    en.wikipedia.org/wiki/Pythagorean_theorem

    using the trigonometric product-to-sum formulas. This formula is the law of cosines , sometimes called the generalized Pythagorean theorem. [ 37 ] From this result, for the case where the radii to the two locations are at right angles, the enclosed angle Δ θ = π /2, and the form corresponding to Pythagoras' theorem is regained: s 2 = r 1 2 ...

  8. Sums of powers - Wikipedia

    en.wikipedia.org/wiki/Sums_of_powers

    In mathematics and statistics, sums of powers occur in a number of contexts: . Sums of squares arise in many contexts. For example, in geometry, the Pythagorean theorem involves the sum of two squares; in number theory, there are Legendre's three-square theorem and Jacobi's four-square theorem; and in statistics, the analysis of variance involves summing the squares of quantities.

  9. Cochran's theorem - Wikipedia

    en.wikipedia.org/wiki/Cochran's_theorem

    (To calculate it, first diagonalize , change into that frame, then use the fact that the characteristic function of the sum of independent variables is the product of their characteristic functions.) For X T Q X {\displaystyle X^{T}QX} and X T Q ′ X {\displaystyle X^{T}Q'X} to be equal, their characteristic functions must be equal, so Q , Q ...