Rule of Twelfths


Lesson abstract

Students learn about the rule of twelfths, a practical way to calculate tidal heights used by many sailors. They apply the rule to graph tidal heights and observe that the graph resembles a sinusoidal curve. They extend their knowledge by comparing the results obtained using the rule of twelfths to actual values of the sine of various angles.

Mathematical purpose

Students learn that tidal patterns closely match a sine curve and use a well-known rule of thumb based to approximate tidal heights. They develop a deeper understanding and appreciation of the properties of the sine curve and its real life occurrences.