The depth (in feet) of water at a dock changes with the rise and fall of tides. The depth is modeled by the function 9T D(t) = 4 cos t+ +5 4 where t is the number of hours after midnight. Find the...

The depth (in feet) of water at a dock changes with the rise and fall of tides. The depth is modeled by the function

Extracted text: The depth (in feet) of water at a dock changes with the rise and fall of tides. The depth is modeled by the function 9T D(t) = 4 cos t+ +5 4 where t is the number of hours after midnight. Find the rate at which the depth is changing at 2 a.m. Round your answer to 4 decimal places.