Classification Of Discontinuities
Continuous functions are of utmost importance in mathematics, functions and applications. However, not all functions are continuous. If a function is not continuous at a point in its domain, one says that it has a discontinuity there. The set of all points of discontinuity of a function may be a discrete set, a dense set, or even the entire domain of the function. This article describes the classification of discontinuities in the simplest case of functions of a single real variable taking real values. The oscillation of a function at a point quantifies these discontinuities as follows: * in a removable discontinuity, the distance that the value of the function is off by is the oscillation; * in a jump discontinuity, the size of the jump is the oscillation (assuming that the value ''at'' the point lies between these limits of the two sides); * in an essential discontinuity, oscillation measures the failure of a limit to exist; the limit is constant. A special case is if the fu ...
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Continuous Function
In mathematics, a continuous function is a function such that a continuous variation (that is a change without jump) of the argument induces a continuous variation of the value of the function. This means that there are no abrupt changes in value, known as '' discontinuities''. More precisely, a function is continuous if arbitrarily small changes in its value can be assured by restricting to sufficiently small changes of its argument. A discontinuous function is a function that is . Up until the 19th century, mathematicians largely relied on intuitive notions of continuity, and considered only continuous functions. The epsilon–delta definition of a limit was introduced to formalize the definition of continuity. Continuity is one of the core concepts of calculus and mathematical analysis, where arguments and values of functions are real and complex numbers. The concept has been generalized to functions between metric spaces and between topological spaces. The latter are t ...
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One-sided Limit
In calculus, a one-sided limit refers to either one of the two limits of a function f(x) of a real variable x as x approaches a specified point either from the left or from the right. The limit as x decreases in value approaching a (x approaches a "from the right" or "from above") can be denoted: \lim_f(x) \quad \text \quad \lim_\,f(x) \quad \text \quad \lim_\,f(x) \quad \text \quad f(x+) The limit as x increases in value approaching a (x approaches a "from the left" or "from below") can be denoted: \lim_f(x) \quad \text \quad \lim_\, f(x) \quad \text \quad \lim_\,f(x) \quad \text \quad f(x-) If the limit of f(x) as x approaches a exists then the limits from the left and from the right both exist and are equal. In some cases in which the limit \lim_ f(x) does not exist, the two one-sided limits nonetheless exist. Consequently, the limit as x approaches a is sometimes called a "two-sided limit". It is possible for exactly one of the two one-sided limits to exist (while t ...
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Regulated Function
In mathematics, a regulated function, or ruled function, is a certain kind of well-behaved function of a single real variable. Regulated functions arise as a class of integrable functions, and have several equivalent characterisations. Regulated functions were introduced by Nicolas Bourbaki in 1949, in their book "Livre IV: Fonctions d'une variable réelle". Definition Let ''X'' be a Banach space with norm , , - , , ''X''. A function ''f'' : , ''T''→ ''X'' is said to be a regulated function if one (and hence both) of the following two equivalent conditions holds true: * for every ''t'' in the interval , ''T'' both the left and right limits ''f''(''t''−) and ''f''(''t''+) exist in ''X'' (apart from, obviously, ''f''(0−) and ''f''(''T''+)); * there exists a sequence of step functions ''φ''''n'' : , ''T''→ ''X'' converging uniformly to ''f'' (i.e. with respect to the supremum norm , , - , , ∞). It requires a little work to show that these two conditions are equi ...
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Riemann Integral
In the branch of mathematics known as real analysis, the Riemann integral, created by Bernhard Riemann, was the first rigorous definition of the integral of a function on an interval. It was presented to the faculty at the University of Göttingen in 1854, but not published in a journal until 1868. For many functions and practical applications, the Riemann integral can be evaluated by the fundamental theorem of calculus or approximated by numerical integration. Overview Let be a non-negative real-valued function on the interval , and let be the region of the plane under the graph of the function and above the interval . See the figure on the top right. This region can be expressed in set-builder notation as S = \left \. We are interested in measuring the area of . Once we have measured it, we will denote the area in the usual way by \int_a^b f(x)\,dx. The basic idea of the Riemann integral is to use very simple approximations for the area of . By taking better and ...
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Froda's Theorem
In the mathematical field of analysis, a well-known theorem describes the set of discontinuities of a monotone real-valued function of a real variable; all discontinuities of such a (monotone) function are necessarily jump discontinuities and there are at most countably many of them. Usually, this theorem appears in literature without a name. It is called Froda's theorem in some recent works; in his 1929 dissertation, Alexandru Froda stated that the result was previously well-known and had provided his own elementary proof for the sake of convenience. Prior work on discontinuities had already been discussed in the 1875 memoir of the French mathematician Jean Gaston Darboux. Definitions Denote the limit from the left by f\left(x^-\right) := \lim_ f(z) = \lim_ f(x-h) and denote the limit from the right by f\left(x^+\right) := \lim_ f(z) = \lim_ f(x+h). If f\left(x^+\right) and f\left(x^-\right) exist and are finite then the difference f\left(x^+\right) - f\left(x^-\right) ...
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Countable
In mathematics, a set is countable if either it is finite or it can be made in one to one correspondence with the set of natural numbers. Equivalently, a set is ''countable'' if there exists an injective function from it into the natural numbers; this means that each element in the set may be associated to a unique natural number, or that the elements of the set can be counted one at a time, although the counting may never finish due to an infinite number of elements. In more technical terms, assuming the axiom of countable choice, a set is ''countable'' if its cardinality (its number of elements) is not greater than that of the natural numbers. A countable set that is not finite is said countably infinite. The concept is attributed to Georg Cantor, who proved the existence of uncountable sets, that is, sets that are not countable; for example the set of the real numbers. A note on terminology Although the terms "countable" and "countably infinite" as defined here are quite c ...
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Complex Analysis
Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch of mathematical analysis that investigates Function (mathematics), functions of complex numbers. It is helpful in many branches of mathematics, including algebraic geometry, number theory, analytic combinatorics, applied mathematics; as well as in physics, including the branches of hydrodynamics, thermodynamics, and particularly quantum mechanics. By extension, use of complex analysis also has applications in engineering fields such as nuclear engineering, nuclear, aerospace engineering, aerospace, mechanical engineering, mechanical and electrical engineering. As a differentiable function of a complex variable is equal to its Taylor series (that is, it is Analyticity of holomorphic functions, analytic), complex analysis is particularly concerned with analytic functions of a complex variable (that is, holomorphic functions). History Complex analysis is one of the classical ...
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Essential Singularity
In complex analysis, an essential singularity of a function is a "severe" singularity near which the function exhibits odd behavior. The category ''essential singularity'' is a "left-over" or default group of isolated singularities that are especially unmanageable: by definition they fit into neither of the other two categories of singularity that may be dealt with in some manner – removable singularities and poles. In practice some include non-isolated singularities too; those do not have a residue. Formal description Consider an open subset U of the complex plane \mathbb. Let a be an element of U, and f\colon U\setminus\\to \mathbb a holomorphic function. The point a is called an ''essential singularity'' of the function f if the singularity is neither a pole nor a removable singularity. For example, the function f(z)=e^ has an essential singularity at z=0. Alternative descriptions Let \;a\; be a complex number, assume that f(z) is not defined at \;a\; but i ...
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Discontinuity Essential
Discontinuity may refer to: * Discontinuity (casting), an interruption in the normal physical structure or configuration of an article * Discontinuity (geotechnical engineering), a plane or surface marking a change in physical or chemical properties in a soil or rock mass * Discontinuity (mathematics), a property of a mathematical function * Discontinuity (linguistics), a property of tree structures in theoretical linguistics * Discontinuity (Postmodernism), a conception of history as espoused by the philosopher Michel Foucault. * Revolutionary breach of legal continuity *A break in continuity (fiction), in literature *Fracture (geology), discontinuity in rocks *Discontinuity (transmission lines) A signal travelling along an electrical transmission line will be partly, or wholly, reflection (physics), reflected back in the opposite direction when the travelling signal encounters a discontinuity (mathematics), discontinuity in the charact ...

Discontinuity Jump
Discontinuity may refer to: * Discontinuity (casting), an interruption in the normal physical structure or configuration of an article * Discontinuity (geotechnical engineering), a plane or surface marking a change in physical or chemical properties in a soil or rock mass * Discontinuity (mathematics), a property of a mathematical function * Discontinuity (linguistics), a property of tree structures in theoretical linguistics * Discontinuity (Postmodernism), a conception of history as espoused by the philosopher Michel Foucault. * Revolutionary breach of legal continuity *A break in continuity (fiction), in literature *Fracture (geology), discontinuity in rocks *Discontinuity (transmission lines) A signal travelling along an electrical transmission line will be partly, or wholly, reflection (physics), reflected back in the opposite direction when the travelling signal encounters a discontinuity (mathematics), discontinuity in the charact ...