One of the most interesting objectives in the experimental sciences is to be able to adequately describe a variable y (dependent variable or response variable) as a function of another variable x (independent variable or explanatory variable). Mathematical functions are a basic tool to describe the dependence of some variables with respect to others. Many of the functions that are used in science can be described analytically from what are called elementary functions. Therefore, it is very important to know the fundamental properties and the graphic representation of the most common elementary functions, such as linear, polynomial, exponential, logarithmic and trigonometric functions.
The main characteristic of a natural process is its evolution over time, and the derivative is a measure that quantifies the change of one variable with respect to another. So the derivatives with respect to time describe the way in which a changing system evolves. In the environmental sciences systems are changing, so the derivative of a function has a wide variety of utilities, the most important in this context is its use in the search for models that describe environmental phenomena. It also includes a topic that contains a small introduction of real functions of several variables, the definition of partial derivatives and their application in non-linear discrete models.