Question

The water depth on August 1st at a certain location in English Bay is modelled by the function

D(t) = 3 + 2 cos (0.5t − 3.4))
where D(t) is the depth of the water (in metres) t hours after midnight.
[2] (a) At 7am, is the tide coming in or going out? How quickly?
[3] (b) At what time(s) over the course of the day does the tide reach its maximum (high tide)? its

minimum (low tide)?

Answer 1