De Moivre's formulaIn 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 holds that where i is the imaginary unit (i2 = −1). The formula is named after Abraham de Moivre, although he never stated it in his works. The expression cos x + i sin x is sometimes abbreviated to cis x. The formula is important because it connects complex numbers and trigonometry.
Jensen's formulaIn the mathematical field known as complex analysis, Jensen's formula, introduced by , relates the average magnitude of an analytic function on a circle with the number of its zeros inside the circle. It forms an important statement in the study of entire functions. Suppose that is an analytic function in a region in the complex plane which contains the closed disk of radius about the origin, are the zeros of in the interior of (repeated according to their respective multiplicity), and that .
Positive-definite functionIn mathematics, a positive-definite function is, depending on the context, either of two types of function. Let be the set of real numbers and be the set of complex numbers. A function is called positive semi-definite if for any real numbers x1, ..., xn the n × n matrix is a positive semi-definite matrix. By definition, a positive semi-definite matrix, such as , is Hermitian; therefore f(−x) is the complex conjugate of f(x)). In particular, it is necessary (but not sufficient) that (these inequalities follow from the condition for n = 1, 2.
Binomial seriesIn mathematics, the binomial series is a generalization of the polynomial that comes from a binomial formula expression like for a nonnegative integer . Specifically, the binomial series is the Taylor series for the function centered at , where and . Explicitly, where the power series on the right-hand side of () is expressed in terms of the (generalized) binomial coefficients If α is a nonnegative integer n, then the (n + 2)th term and all later terms in the series are 0, since each contains a factor (n − n); thus in this case the series is finite and gives the algebraic binomial formula.
Formal distributionIn mathematics, a formal distribution is an infinite sum of powers of a formal variable, usually denoted in the theory of formal distributions. The coefficients of these infinite sums can be many different mathematical structures, such as vector spaces or rings, but in applications most often take values in an algebra over a field. These infinite sums are allowed to have infinitely many positive and negative powers, and are not required to converge, and so do not define functions of the formal variable.
Cauchy–Riemann equationsIn the field of complex analysis in mathematics, the Cauchy–Riemann equations, named after Augustin Cauchy and Bernhard Riemann, consist of a system of two partial differential equations which form a necessary and sufficient condition for a complex function of a complex variable to be complex differentiable. These equations are and where u(x, y) and v(x, y) are real differentiable bivariate functions.
Colin MaclaurinColin Maclaurin (məˈklɔːrən; Cailean MacLabhruinn; February 1698 – 14 June 1746) was a Scottish mathematician who made important contributions to geometry and algebra. He is also known for being a child prodigy and holding the record for being the youngest professor. The Maclaurin series, a special case of the Taylor series, is named after him. Owing to changes in orthography since that time (his name was originally rendered as M'Laurine), his surname is alternatively written MacLaurin. Maclaurin was born in Kilmodan, Argyll.
Constant termIn mathematics, a constant term (sometimes referred to as a free term) is a term in an algebraic expression that does not contain any variables and therefore is constant. For example, in the quadratic polynomial the 3 is a constant term. After like terms are combined, an algebraic expression will have at most one constant term. Thus, it is common to speak of the quadratic polynomial where is the variable, as having a constant term of If the constant term is 0, then it will conventionally be omitted when the quadratic is written out.
Lambert W functionIn mathematics, the Lambert W function, also called the omega function or product logarithm, is a multivalued function, namely the branches of the converse relation of the function f(w) = wew, where w is any complex number and ew is the exponential function. For each integer k there is one branch, denoted by Wk(z), which is a complex-valued function of one complex argument. W0 is known as the principal branch.
Harmonic numberIn mathematics, the n-th harmonic number is the sum of the reciprocals of the first n natural numbers: Starting from n = 1, the sequence of harmonic numbers begins: Harmonic numbers are related to the harmonic mean in that the n-th harmonic number is also n times the reciprocal of the harmonic mean of the first n positive integers. Harmonic numbers have been studied since antiquity and are important in various branches of number theory.
