*World of Mathematics*. ©2005-2006 Thomson Gale, a part of the Thomson Corporation. All rights reserved.

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## Function

A function represents a mathematical relationship between two **sets** of **real numbers**. These sets of numbers are related to each other by a rule which assigns each value from one set to exactly one value in the other set. The standard notation for a function y = f(x), developed in the 18th century, is read "y equals f of x." Other representations of functions include graphs and tables. Functions are classified by the types of rules which govern their relationships including; algebraic, trigonometric, and logarithmic and exponential. It has been found by mathematicians and scientists alike that these **elementary functions** can represent many real-world phenomena.

## History of functions

The idea of a function was developed in the 17th century. During this time, Rene Descartes (1596-1650), in his book *Geometry* (1637), used the concept to describe many mathematical relationships. The term "function" was introduced by Gottfried Wilhelm Leibniz (1646-1716) almost...

This section contains 1,249 words(approx. 5 pages at 300 words per page) |