Explain how to determine the following from the graph:
number of times the barnacle went beneath the water level if the boat traveled a distance of 20 m
number of meters of the 20 m trip that the barnacle was underwater
determine by the number of times the barnacle using the cos theorem. number of meters of the 20 m trip by plotting the points on a graph

-when the graph is below the x-axis, the barnacle is underwater.
-the graph dips below the x-axis three times between x = 0 and x = 20, so the barnacle goes underwater three times.
-every time the barnacle goes underwater, the boat travels pie meters (one half the circumference of the wheel) before the barnacle comes back up, so the barnacle covers 3 pie meters underwater between x = 0 and x = 20.