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:For distance between people, see proxemics.

1 Distance between two points

The distance between two points is the length of a straight line between them. In the case of two locations on Earth, usually the distance along the surface is meant: either " as the crow flies" (along a great circle) or by road, railroad, etc. Distance is sometimes expressed in terms of the time to cover it, for example walking or by car. Sometimes a distance thus indicated is ambiguous because the means of transport is neither mentioned nor obvious.

Distance as mentioned above is sometimes not symmetric, hence not a metric (see below): this applies to distance by car in the case of one-way streets, and also in the case the distance is expressed in terms of the time to cover it (a road may be more crowded in one direction than in the other, for a ship upstream and downstream makes a difference).

As opposed to a position coordinate, a distance can not be negative. Distance is a scalar quantity, containing only a magnitude, whereas displacement is an equivalent vector quantity containing both magnitude and direction.

2 Distance covered


The distance covered by a vehicle (often recorded by a odometer), person, animal, object, etc. should be distinguished from the distance from starting point to end point, even if latter is taken to mean e.g. the shortest distance along the road, because a detour could be made, and the end point can even coincide with the starting point.

3 Distance in mathematics

In mathematicsMathematics is commonly defined as the study of patterns of structure, change, and space; more informally, one might say it is the study of "figures and numbers". In the formalist view, it is the investigation of axiomatically defined abstract structures, a distance between two points P and Q in a metric spaceIn mathematics, a metric space is a set (or "space") where a distance between points is defined. History Maurice Frechet introduced metric spaces in his work Sur quelques points du calcul fonctionnel Rendic. Palermo 22(1906) 1-74. Formal definition Formal is d(P,Q), where d is the distance function. We can also define the distance between two sets A and B in a metric space as being the minimum (or infimumIn mathematics the infimum of a subset of some set is the greatest element that is smaller than all other elements of the subset. Consequently the term greatest lower bound is also commonly used. Infima of real numbers are a common special case that is es) of distances between any two points P in A and Q in B.

4 The distance formula

The distance, d, between two points expressed in Cartesian coordinatesCartesian means relating to the French mathematician and philosopher Descartes, who, among other things, worked to merge algebra and Euclidean geometry. This work was influential to the development of analytic geometry, calculus, and cartography. The idea equals the square rootIn mathematics, the square root of a non-negative real number is denoted and represents the non-negative real number whose square (the result of multiplying the number by itself) is. For example, since. This example suggests how square roots can arise whe of the sum of the squares of the changes of each coordinate. Thus, in a two-dimensional space,


...and in a three-dimensional space:


"Δ" (delta) refers to the change in a variable. Thus, Δx is the change in x, pronounced as such, or as "delta-x". In mathematical terms, .

This distance formulaA formula is a concise way of expressing information symbolically (as in a mathematical or chemical formula) or a general relationship between quantities. A famous one is Albert Einstein's E m × c 2 (see Special relativity). See also WikiMath: how to writ can be seen as a specialized form of the Pythagorean theoremIn mathematics, the Pythagorean theorem or Pythagoras's theorem is a relation in Euclidean geometry between the three sides of a right triangle. The theorem is named after and commonly attributed to the 6th century BC Greek philosopher and mathematician P; it can also be expanded into the arc-length formulaEdge may have one of the following special meanings, in addition to its dictionary definition: wiktionary:edge. In graph theory, a graph shows a set of connections between objects. Each object is a vertex. Each connection, between two vertices, forms an e.





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