Posts Tagged ‘function’
Tuesday, January 5th, 2010
An Overview of the Cantor-Bernstein-Schroeder Theorem
Description
A detailed tutorial on the Cantor-Bernstein-Schroeder Theorem. Step by step tutorial including several examples of the Cantor-Bernstein-Schroeder Theorem for reference.
Overview
The Cantor-Bernstein-Schroeder Theorem states that if there exist injective functions f: A –> B and g: B –> A between the sets A and B, then there exists a bijective function h: A –> B. This means that if |A| < |B| and |B| < |A|, then they are equipollent. Equipollent is a term that is similar to equal, and is denoted in the same way. However, the word equipollent means equal in cardinality, but not in any other way.
Tags: Bernstein, bijective, Cantor, cardinality, denoted, discrete math, equal, equipollent, Ernst, Felix, function, Georg, injective, Schroeder, theorem
Posted in Discrete Math | No Comments »
Thursday, December 31st, 2009
How to Write Step Functions
Description
A detailed tutorial on how to write step functions. Step by step tutorial including several examples of how to write step functions for reference.
Overview
A step function, also called a staircase function, is a finite linear combination composed of several different intervals. They are considered to be a piecewise constant function. The graph of a step function is often expressed as steps, or a staircase, which is how it got its name. It simply looks like several disconnected lines, with alternate open and closed ends so that it easily passes the vertical line test for functions.
Tags: closed, combination, constant, diconnected, discrete math, ends, finite, function, graph, intervals, line, linear, lines, open, piecewise, staircase, step, test, vertical
Posted in Discrete Math | No Comments »
Thursday, December 24th, 2009
Finding the Function of a Directed Graph
Description
A detailed tutorial on finding the function of a directed graph. Step by step tutorial including several examples of finding functions of digraphs for reference.
Overview
A directed graph, more commonly known as a digraph, is the visual representation of a function or of a relation. As in any graph, there are points and lines – called vertices and edges in a digraph. Each edge has an arrow pointing to a vertex. The first vertex – the one the arrow comes from – is the x coordinate of an ordered pair. The second vertex – the one the arrow is pointing to – is the y coordinate of an ordered pair. In the case of double-sided arrows, two ordered pairs are made, with the x and y coordinates switching. This is done for every single vertex and edge on the graph.
Tags: arrow, coordinate. ordered, digraph, directed, discrete math, double, edges, expression, First, function, graph, lines, pair, points, relation, representation, second, side, vertex, vertices, visual, x, y
Posted in Discrete Math | No Comments »
Thursday, December 10th, 2009
Inverse Image of Sets
Description
A detailed tutorial on the inverse image of sets. Step by step tutorial on the inverse image of sets for reference. Knowledge of the inverse image of sets is important in advanced discrete mathematics courses.
Overview
Say that you have a function f: A –> B. Then, X is a subset of A and Y is a subset of B. The image of X or the image set of X is f(X) = {y belongs to B: y = f(x) for some x belonging to X}. The inverse image of Y is defined as f^-1(Y) = {x belongs to A: f(x) belongs to Y}. The inverse image is simply a reversed form of the image. Often when asked to find the inverse image, it will help to set up a drawing of the image of the function, connecting everything where it needs to go. Then to find the inverse you simply reverse your work.
Tags: a, b, connect, diagram, discrete math, form, function, image, image set, inverse, mapping, picture, reverse, set, subset, x, y
Posted in Discrete Math | No Comments »
Friday, November 20th, 2009
Overview of the Vertices of a Graph
Description
A detailed tutorial on the vertices of a grpah. Step by step tutorial including several examples of the vertices of a graph for reference.
Overview
The vertices of a graph are the number of lines extending from points on the graph. This is not the total number of edges – it is the number of edges extending from each point all added together. Each point has at least one vertex. Not every single point can have an odd number of vertices, and all the vertices cannot add up to an odd number, or it is not considered to be the graph of a function.
Tags: add, discrete math, edges, even, extending, function, graph, line, odd, point, vertex, vertices
Posted in Discrete Math | No Comments »
Friday, November 20th, 2009
Overview of the Preimage of a Set
Description
A detailed tutorial on the preimage of a set. Step by step tutorial including several examples of the preimage of a set for reference.
Overview
The preimage of a set is defined over a function. If there is a function over A and B, then we can say that y = f(x), provided that (x, y) belongs to f. Based on this definition, x is the preimage of y under f. To find the preimage, simply look for the value of x that matches with the proper value of y in any function of ordered pairs in A and B.
Tags: a, b, belongs, coordinates, defined, definition, discrete math, f, function, image, ordered pairs, preimage, set, theory, value, x, y
Posted in Discrete Math | No Comments »
Thursday, November 19th, 2009
Defining the Angles Between Vectors
Description
A detailed tutorial on how to define the angles between vectors. Step by step tutorial including several examples of angles between vectors for reference.
Overview
In general, it is easier to find the angle between 2D vectors, rather than 3D vectors. In order to define the angles between vectors, we need to use the dot product in conjunction with a few other functions. The angles between vectors can be expressed as angle = arccos(v1xv2), where v1xv2 is how the dot product is expressed.
Tags: 2D, 3D, absolute, algebra, angle, arccos, conjunction, cosine, define, degrees, dot, function, linear, magnitude, product, radians, value, vector
Posted in Algebra | No Comments »
Thursday, November 19th, 2009
Overview of Revenue, Cost, and Product Functions
Description
A detailed tutorial on revenue, cost, and product functions. Step by step tutorial including several examples of revenue, cost, and product functions for reference.
Overview
The revenue, cost, and product functions are parts of economics and business math. The cost function is how much something costs, and it can be expressed as C(q) = 100 + 2q. The revenue function is how much money you get from selling what you bought, and it can be expressed as R(q) = 2.5q. The profit function is how much money was actually made, and it is the revenue function minus the cost function.
Tags: algebra, business, cost, economics, function, gained, lost, Math, money, product, revenue, subtraction
Posted in Algebra | No Comments »
Thursday, November 19th, 2009
Overview of the Cost Function
Description
A detailed tutorial on the cost function. Step by step tutorial including several examples of the cost function for reference.
Overview
The cost function is a name for a function that is being used in optimization. It is a very important part of an optimization problem. The cost function can be any graph, because all it refers to is the function – the function could be different every time, and it could still be called the cost function. What we learn from this is that the cost function is not unique.
Tags: algebra, constraints, cost, domain, energy, function, functional, graph, linear, maximize, minimize, objective, optimization, solution, unique, variable
Posted in Algebra | No Comments »
Tuesday, November 17th, 2009
Overview of Green’s Function
Description
A detailed tutorial on Green’s function. Step by step tutorial including several examples of Green’s function for reference.
Overview
Green’s function is used in deifferential equations as a method of solving certain types of equations that are subject to boundary conditions. There equations are called inhomogeneous differential equations. Unlike many other functions, Green’s function is not studied by how to use it to solve equations, but it is studied by the fundamental solutions.
Tags: boundary, conditions, differential, differential equations, equations, function, fundamental, George Green, Green's function, inhomogeneous, solutions
Posted in Differential Equations | No Comments »
