Graphs provide a means to visualize a mathematical set, function, or even set of functions. Objects depicted in a graph may be one-dimensional, such as a number line; two-dimensional, such as a parabola, or three-dimensional, such as a sphere. Graphs are used extensively throughout the fields of mathematics, statistics, science, engineering, business, and research in order to depict information--whether a mathematical curve of statistical data--in a form that humans find easy to process. Graphs provide a means to quickly assimilate information--and even trends present in the information--in a more intuitive way than reviewing long lists of numerical data.

Domain

The domain of a function, often symbolized by an italicized capital D, is the set of values over which the function exists. The set of values is generally connected (that is, continuous, such as all values in the closed interval [-1, 1]), but may...