BROWSE ALPHABETICALLY LEVEL:    Elementary    Advanced    Both INCLUDE TOPICS:    Basic Math    Algebra    Analysis    Biography    Calculus    Comp Sci    Discrete    Economics    Foundations    Geometry    Graph Thry    History    Number Thry    Phys Sci    Statistics    Topology    Trigonometry function – identity map function   Given a binary relation R on sets A and B, we say that the R is a function if each element of A is paired with at most one element of B. In this case we call A the domain set, and we call B the range set. If f is such a function and the ordered pair (x,y) is an element of the function, we typically write f(x) = y.More generally, if R is an n-place relation, then R is a function of n-1 variables if each (n-1)-tuple is matched with at most one element of the range set (i.e., the nth set of the Cartesian product on which the relation is defined). If in addition there is at most one element of the domain set matched with any given element of the range set, then the function is called “one-to-one” or injective. If the function maps at least one element of the domain set to every element of its range set, then it is called “onto” or surjective. A function which is both injective and surjective is called bijective. Functions with range in the real numbers or complex numbers are called real-valued or complex-valued respectively. Fundamental Theorem of Algebra   The field of complex numbers is algebraically closed, that is, any polynomial with complex coefficients has a complex root. Fundamental Theorem of Arithmetic    ARTICLE   Every natural number is either prime or may be decomposed uniquely into prime factors. Fundamental Theorem of Calculus   Intitively, that the integral and derivative are inverse operatorations on functions. The fundamental theorem is commonly expressed in either one of two formal guises:Cf. Riemann integral. g.c.d.   Abbreviation for greatest common divisor. geodesic   A curve on a space is a geodesic if, given any two points on the curve, the segment of the curve joining the points is the shortest such curve. In Euclidean space, geodesics are straight lines. On a sphere, the geodesics are the great circles of the sphere.Graph Theory: A shortest path between two vertices is sometimes called a geodesic.Cf. distance. geometric series   An infinite series such that the ratio of consecutive terms is constant. Such a series may be denotedwhere r is the common ratio. A geometric series converges if and only if the common ratio is less than 1, in which case the sum of the series is given byCf. arithmetic series, harmonic series. Related article: Series g.l.b.   Abbreviation for greatest lower bound. graph   General: A picture or diagram representing one or more relationships among certain objects or quantities.Functions: The collection of ordered tuples (x,y), consisting of domain elements x (possibly also tuples) and corresponding range elements y. Although informally we often mean the picture when we speak of the graph of a function, the graph should always be formally thought of as a set of tuples.Graph Theory: A collection of nodes (also called vertices), together with a set of edges joining the nodes. Formally, a graph G is a set of vertices V, a set of edges E, and a symmetric relation between them specifying incidence. Every edge must be incident on exactly two (not necessarily distinct) vertices, called its ends. Two vertices incident on the same edge are called adjacent. Graphs are often represented pictorially, with the vertices being points (or small circles or squares or some such), and the edges being curves (often line segments), with the endpoints of each such curve being the ends of that edge in the graph. Cf. Konigsberg Bridge Problem. great circle   On a sphere, a great circle is a circle containing the endpoints of a diameter of the sphere, that is, a circle of maximal size. A geodesic on a sphere always lies on a great circle. greatest common divisor   The greatest common divisor of two natural numbers a and b is the largest natural number c such that c divides a and c divides b. greatest lower bound   A lower bound which is greater than or equal to every other lower bound.Cf. Least upper bound. Greek    ARTICLE   Letters of the Greek alphabet are commonly used in mathematics. See the article for a full description. harmonic series   The infinite series whose terms are the reciprocals of the natural numbersThis series diverges, i.e., the sum does not exist. Related article: Series hexagon   A regular polygon having six equal sides and six equal interior angles. Hexagons can be used to tile the plane, and do so more efficiently than any other polygon.Cf. tesselation. hyperbola   The locus of points in the plane, the difference of whose distances from two fixed points, called the foci, remains constant.Like the ellipse and parabola, the hyperbola is a conic section. Related article: Conics hypotenuse   On a right triangle, the side opposite the right angle. i   See imaginary number. icosahedron   A polyhedron having twenty faces.The faces of a regular icosahedron are congruent, equilateral triangles.Cf. Platonic solid. identity function   A function that maps each domain element to itself. Also called the identity map. identity map function – identity map
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