Not all curves are functions. This applet shows a few curves that are or are not functions. The primary test for a function is the vertical line test. If more than one [math]y[/math] value exist for any [math]x[/math] value, the resulting value cannot be determined. A curve that is not a function still represents a relation. Examples are shown in the applet.[br]Click the next button to advance to the next relation.[br]For the last relation, five black points can be used to modify the relation.

For each relation move the [math]x[/math] value and note the domain and range of the relations that are functions.[br]All of the relations in this applet are conic sections, can you have other types of relations that are not functions?