Let be a real function of a real variable , defined over a domain in . The set of points in the plane whose coordinates are , for is called the graph of .
The curves in figure 4 are not graphs of functions. Dear reader, why?
We will make great use of graphs. On the one hand, they provide a good visual intuition of the phenomena described by the fuctions. On the other hand, applied scientists are often able to draw a graph representing the phenomenon that they study, even when the actual function is still unknown. From the study of the graph they can get many useful conclusions.
Noah Dana-Picard 2007-12-28