# Rate of change

A series of swells passes through a group of surfers. They notice that for a few minutes, the waves pass through at regular intervals: every 14 seconds. Let t=0 be the time when the wave is at its lowest point. The maximum instantaneous increase in height of the wave is 2.25 feet per second.

a. Find r(t), the rate of change of the height of the wave above the ocean floor at time t seconds.

b. If the bottom of the wave is 8 feet above the ocean floor, find h(t), the height of the wave at time t.

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#### Solution Preview

a)

The height of the wave varies sinusoidally, with period T = 14 s.

The instantaneous increase in height at t=0 is 0, so the rate of change of the height of the wave must be of the form

r(t) ...

#### Solution Summary

This shows how to find the rate of change of height and the height at a point in time for waves with a given situation.