Question

The height in metres of the water in a harbour is given approximately by the formula d=6+3cos30t, where t is the time in hours from. Find
a) The height if the water at 9:45pm
b) The highest and the lowest water level and occur
"where t is the time in hours from....." is incomplete
Did you mean from noon ?

Let's assume it is after noon, else make the necessary adjustments
at 9:45 pm , t = 9.75
set your calculator to radians
d = 3.163 metres

The min of 3cos 30t is -3 and its max is +3
So the max height is 9 m and the lowest is 3
Can you please explain to me why the maximum value of d occurs when the value of the cosine function is 1?
Thank you
*Sadie* cauz For cosine's graph the range is from -1 to 1, u can check it out at desmos graph!!! REGARDLES of the fact that its 2 years later (:

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