Question 0.1.16: Using the Vertical Line Test Determine which of the curves i...

Notice that the circle in Figure 0.18a is not the graph of a function, since a vertical line at x = 0.5 intersects the circle twice. (See Figure 0.19a.) The graph in Figure 0.18b is the graph of a function, even though it swings up and down repeatedly. Although horizontal lines intersect the graph repeatedly, vertical lines, such as the one at x = 1.2, intersect only once. (See Figure 0.19b.)