Graphs as functions One of the notations for functions is to show the ordered pairs on a graph. We can use the graph and the vertical line test to determine if the graph is a function. The vertical line test allows you to drop a vertical line anywhere on the graph and cross the function line only once. Take a piece of spaghetti and move it vertically along the entire graph. It should touch the graph at only one place at all times. Example: The first diagram shows a vertical line test that demonstrates a function. The second diagram shows a vertical line test that does not demonstrate a functions.
Fig. 1
Fig. 2
Use a string a piece of spaghetti, or a ruler to create a vertical line. Test each of the graphs to determine if each one is a function or not. If it is not a function, mark the places where the vertical line touches more than once.