# Modeling/Solving Trigonometric Equation

**Question description**

Given: *y* = *A *cos(*Bx* − *C*) + *D*. The depth of water at the end of a pier varies with the tides. High tide = 4 a.m. w/ a depth of 6 meters. Low tide = 10 a.m. w/ a depth of 2 meters.

A. Model the problem by using the given trigonometric equation to show the depth of the water *t *hours after midnight, showing all your work.

B. Solve the problem by finding the depth of the water at noon, explaining your reasoning.

C. A large boat needs at least 4 meters of water to secure it at the end of the pier. Determine what span of time after noon, including both a starting and ending time, the boat can first safely be secured, justifying your answer.

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