Have graph paper readily available. Before starting work on Problems A1-A5, keep in mind that the graph will have the height of the tide on the y-axis. The "change in tide" column in the table is just to help you create the third column. The computations, though they deal with fractions (multiples of 1/12), should not be difficult, because the height of the tide is a multiple of 12.
Groups: Share graphs by tracing them on overheads. Discuss how this problem is an example of a cyclic function. Think of other examples of things that go in cycles. Examples include the motion of the planets and radio waves.
Think about the concepts of amplitude and period, two ideas that are an important part of the study of cyclic functions. Depending on where you are, the amplitude of tides can vary greatly, although the period is always the same.
Groups: If time allows, sketch graphs for tides in different places around the world. Discuss what would vary and what wouldn't.
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