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In mathematics, de Moivre's formula (also known as de Moivre's theorem and de Moivre's identity) states that for any real number x and integer n it is the case that ( + ) = + , where i is the imaginary unit (i 2 = −1).
where θ is the angle whose cosine is α / M and whose sine is β / M ; the last equality here made use of de Moivre's formula. Now the process of finding the coefficients c j and c j+1 guarantees that they are also complex conjugates, which can be written as γ ± δi. Using this in the last equation gives this expression for ...
Historically, the first four of these were known as Werner's formulas, after Johannes Werner who used them for astronomical calculations. [29] See amplitude modulation for an application of the product-to-sum formulae, and beat (acoustics) and phase detector for applications of the sum-to-product formulae.
de Moivre's illustration of his piecewise linear approximation. De Moivre's law first appeared in his 1725 Annuities upon Lives, the earliest known example of an actuarial textbook. [6] Despite the name now given to it, de Moivre himself did not consider his law (he called it a "hypothesis") to be a true description of the pattern of human ...
For examples of trigonometric functions as generating functions in combinatorics, see Alternating permutation. Dirichlet kernel; ... De Moivre's formula; Euler's formula;
That cos nx is an n th-degree polynomial in cos x can be seen by observing that cos nx is the real part of one side of de Moivre's formula: + = ( + ). The real part of the other side is a polynomial in cos x and sin x , in which all powers of sin x are even and thus replaceable through the identity cos 2 x + sin 2 x = 1 .
According to the de Moivre–Laplace theorem, as n grows large, the shape of the discrete distribution converges to the continuous Gaussian curve of the normal distribution. In probability theory , the de Moivre–Laplace theorem , which is a special case of the central limit theorem , states that the normal distribution may be used as an ...
De Moivre's formula shows that numbers of this form are roots of unity: ... the sine and cosine can be derived with the half-angle formulas. For example, ...