Modeling Periodic Phenomena with Trigonometric Functions

Throughout any given month, the maximum and minimum ocean tides follow a periodic pattern.Last year, at a certain location on the California coast, researchers recorded the height of low tide, with respect to sea level, each day during the month of July.The lowest low tide was first measured on July 11, at -1.4 feet.The highest low tide was first measured on July 4, at 1.8 feet.The average low tide for the month of July was measured to be 0.2 feet.

Part A

Why do the ocean tides follow a periodic pattern?