A metric on a set X is a function (called the distance function or simply distance) d : X × X → R (where R is the set of real numbers). For all x, y, z in X, this function is required to satisfy the following conditions: d(x, y) ≥ 0     (non-negativity) d(x, y) = 0   if and only if   x = y     (identity ...

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Metric mathematics, Metric mathematics - Definition, Metric mathematics - Notes, Metric mathematics - Examples, Metric mathematics - Equivalence of metrics, Metric mathematics - Relation of norms and metrics, Metric mathematics - Related concepts and alternative axiom systems

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Supremum - Greatest elements. The difference between the supremum of a set and the greatest element of a set may not be immediately obvious. The difference is exemplified by the set of negative real numbers. Since 0 is not a negative number, this set has no greatest element: for every element of the set, there is another, larger element. For instance, for any negative real number x, there is a negative real number x/2, which is greater. On the other hand, the upper bounds of the set of negative real ...

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Supremum, Supremum - Supremum of a set of real numbers, Supremum - Approximation property, Supremum - Additive property, Supremum - Comparison property, Supremum - Suprema within partially ordered sets, Supremum - Comparison with other order theoretical notions, Supremum - Greatest elements, Supremum - Maximal elements, Supremum - Minimal upper bounds, Supremum - Least-upper-bound property

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The least-upper-bound property is an example of the aforementioned completeness properties which is typical for the set of real numbers. If an ordered set S has the property that every nonempty subset of S having an upper bound also has a least upper bound, then S is said to have the least-upper-bound property. As noted above, the set R of all real numbers has the least-upper-bound property. Similarly, the set Z of integers has the least-upper-bound property; if S is a nonempty subset o ...

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Supremum, Supremum - Supremum of a set of real numbers, Supremum - Approximation property, Supremum - Additive property, Supremum - Comparison property, Supremum - Suprema within partially ordered sets, Supremum - Comparison with other order theoretical notions, Supremum - Greatest elements, Supremum - Maximal elements, Supremum - Minimal upper bounds, Supremum - Least-upper-bound property

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Infinity - Infinity in real analysis. In real analysis, the symbol , called "infinity", denotes an unbounded limit. means that x grows beyond any assigned value, and means x is eventually less than any assigned value. Points labeled and can be added to the real numbers as a topological space, producing the two-point compactification of the real numbers. Adding algebraic properties to this gives us the extended real numbers. We can also treat and as the same, leading to the one-point compact ...

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Infinity, Infinity - History, Infinity - Ancient view of infinity, Infinity - Views from the Renaissance to modern times, Infinity - Modern philosophical views, Infinity - Infinity symbol, Infinity - Mathematical infinity, Infinity - Infinity in real analysis, Infinity - Infinity in complex analysis, Infinity - Arithmetic properties of infinity, Infinity - Infinity in set theory, Infinity - Mathematics without infinity, Infinity - Use of infinity in common speech, Infinity - Physical infinity, Infinity - Infinity in cosmology, Infinity - Three types of infinities, Infinity - Infinity in science fiction, Infinity - Note

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In common parlance, infinity is often used in a hyperbolic sense. For example, "The movie was infinitely boring, but we had to wait forever to get tickets." In video games, infinite lives and infinite ammo refer to a never-ending supply of lives and ammunition. An infinite loop in computer programming is a conditional loop construction whose condition always evaluates to true. In theory, as long as there is no external interaction, the loop will continue to run for all time. In practice however, most programming loops co ...

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Infinity, Infinity - History, Infinity - Ancient view of infinity, Infinity - Views from the Renaissance to modern times, Infinity - Modern philosophical views, Infinity - Infinity symbol, Infinity - Mathematical infinity, Infinity - Infinity in real analysis, Infinity - Infinity in complex analysis, Infinity - Arithmetic properties of infinity, Infinity - Infinity in set theory, Infinity - Mathematics without infinity, Infinity - Use of infinity in common speech, Infinity - Physical infinity, Infinity - Infinity in cosmology, Infinity - Three types of infinities, Infinity - Infinity in science fiction, Infinity - Note

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In physics, approximations of real numbers are used for continuous measurements and natural numbers are used for discrete measurements (i.e. counting). It is therefore assumed by physicists that no measurable quantity could have an infinite value, for instance by taking an infinite value in an extended real number system (see also: hyperreal number), or by requiring the counting of an infinite number of events. It is for example presumed impossible for any body to have infinite mass or infinite energy. There exists the concept of infinite en ...

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Infinity, Infinity - History, Infinity - Ancient view of infinity, Infinity - Views from the Renaissance to modern times, Infinity - Modern philosophical views, Infinity - Infinity symbol, Infinity - Mathematical infinity, Infinity - Infinity in real analysis, Infinity - Infinity in complex analysis, Infinity - Arithmetic properties of infinity, Infinity - Infinity in set theory, Infinity - Mathematics without infinity, Infinity - Use of infinity in common speech, Infinity - Physical infinity, Infinity - Infinity in cosmology, Infinity - Three types of infinities, Infinity - Infinity in science fiction, Infinity - Note

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To illustrate some of the proof techniques used in Lebesgue integration theory, we sketch a proof of the above mentioned Lebesgue monotone convergence theorem: Let {fk}k ∈ N be a non-decreasing sequence of non-negative measurable functions and put By the monotonicity property of the integral, it is immediate that: We now prove the inequa ...

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Lebesgue integration, Lebesgue integration - Introduction, Lebesgue integration - Construction of the Lebesgue integral, Lebesgue integration - Measure theory, Lebesgue integration - Integration, Lebesgue integration - Intuitive interpretation, Lebesgue integration - Example, Lebesgue integration - Limitations of the Riemann integral, Lebesgue integration - Basic theorems of the Lebesgue integral, Lebesgue integration - Proof techniques, Lebesgue integration - Alternative formulations, Lebesgue integration - Quote

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The Lebesgue integral does not distinguish between functions which only differ on a set of μ-measure zero. To make this precise, functions f, g are said to be equal almost everywhere (or equal a.e.) iff If f, g are non-negative functions (possibly assuming the value +∞) such that f = g almost everywhere, then If f, g are functions such that f = g almost everywhere, then f is integrable iff gSee also:

Lebesgue integration, Lebesgue integration - Introduction, Lebesgue integration - Construction of the Lebesgue integral, Lebesgue integration - Measure theory, Lebesgue integration - Integration, Lebesgue integration - Intuitive interpretation, Lebesgue integration - Example, Lebesgue integration - Limitations of the Riemann integral, Lebesgue integration - Basic theorems of the Lebesgue integral, Lebesgue integration - Proof techniques, Lebesgue integration - Alternative formulations, Lebesgue integration - Quote

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The integral of a function f between limits a and b can be interpreted as the area under the graph of f. This is easy to understand for familiar functions such as polynomials, but what does it mean for more exotic functions? In general, what is the class of functions for which "area under the curve" makes sense? The answer to this question has great theoretical and practical importance. As part of a general movement toward rigour in mathematics in the nineteenth century, attempts were made to put the integr ...

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Lebesgue integration, Lebesgue integration - Introduction, Lebesgue integration - Construction of the Lebesgue integral, Lebesgue integration - Measure theory, Lebesgue integration - Integration, Lebesgue integration - Intuitive interpretation, Lebesgue integration - Example, Lebesgue integration - Limitations of the Riemann integral, Lebesgue integration - Basic theorems of the Lebesgue integral, Lebesgue integration - Proof techniques, Lebesgue integration - Alternative formulations, Lebesgue integration - Quote

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Here we discuss the limitations of the Riemann integral and the greater scope offered by the Lebesgue integral. We presume a working understanding of the Riemann integral. With the advent of Fourier series, many analytical problems involving integrals came up whose satisfactory solution required exchanging infinite summations of functions and integral signs. However, the conditions under which the integrals are equal proved quite elusive in the Riemann framework. There are some other technical difficulties with the Riemann ...

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Lebesgue integration, Lebesgue integration - Introduction, Lebesgue integration - Construction of the Lebesgue integral, Lebesgue integration - Measure theory, Lebesgue integration - Integration, Lebesgue integration - Intuitive interpretation, Lebesgue integration - Example, Lebesgue integration - Limitations of the Riemann integral, Lebesgue integration - Basic theorems of the Lebesgue integral, Lebesgue integration - Proof techniques, Lebesgue integration - Alternative formulations, Lebesgue integration - Quote

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The Hitchhiker's Guide to the Galaxy contains the following definition of infinity: "Bigger than the biggest thing ever and then some, much bigger than that, in fact really amazingly immense, a totally stunning size, real 'Wow, that's big!' time. Infinity is just so big that by comparison, bigness itself looks really titchy. Gigantic multiplied by colossal multiplied by staggeringly huge is the s ...

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Infinity, Infinity - History, Infinity - Ancient view of infinity, Infinity - Views from the Renaissance to modern times, Infinity - Modern philosophical views, Infinity - Infinity symbol, Infinity - Mathematical infinity, Infinity - Infinity in real analysis, Infinity - Infinity in complex analysis, Infinity - Arithmetic properties of infinity, Infinity - Infinity in set theory, Infinity - Mathematics without infinity, Infinity - Use of infinity in common speech, Infinity - Physical infinity, Infinity - Infinity in cosmology, Infinity - Three types of infinities, Infinity - Infinity in science fiction, Infinity - Note

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